"ProPhoto 4" > "Customize" > "Bio" > "Background"
Your ProPhoto Bio Area has two background options: Main and Inner backgrounds. Your main background is the ‘deepest’ background layer and the inner background layer appears on top of the main background. The inner background layer is provided to insert images like the page turn effect seen here:

The main background is a strip of grey gradient tiled horizontally, while the inner background (shown in red) is the page turn image positioned in the upper right.
Both image types are able to span the full width of the site, and can even be tiled to your preference. Using both background images can be used to create some flashy design effects.
General background area instructions:
There are many areas of your blog that allow you to modify their background colors and/or background images. ProPhoto’s interface makes fine-tuning these options a cinch. If the background area already has an image uploaded, you will see these options:

1) There are two general ways for a background image to be displayed, tiled or not tiled. A tiled image can be repeated horizontally, vertically, or both.

Tiled background images are nice because a small image can cover a large background area, keeping load times low. Images that you want to tile over a background should be created especially for tiling or they will probably have a visible seam every time the image repeats. Here is a tutorial on creating a seamless background image: Repeating Seamless Background Image Tutorial
2) When displaying a background image, you can determine where that the image will be shown.

Let’s say you are adding a background image to your blog’s outer background area. Choosing “top center” for an image that is being tiled vertically will repeat your image vertically as a strip down the center of your blog’s background.
3) Tell your background whether or not to scroll vertically with your blog content. An image that is not tiled and positioned “top center” can be set to “stay fixed in place” so that the background image will always stay at the top of the browser, even when visitors scroll down your blog content. (This option is only relevant for your blog’s outer background).

Fixed: When scrolled to bottom of blog, the outer background image stays in place.
You can see a live example of this here: Elegant Design
4) Set color of a background area. Background colors are always displayed behind any background image applied to the same element. If you set your background image to “tiled”, you won’t see your background color at all. If your image isn’t tiled, your background color will be visible beyond the edges of the background image. You can see this effect in the screenshot below, where a large background image was uploaded and set to “tile only horizontally”, “top center” and “fixed”.

The green box shows the background image. Outside of that, you are seeing the bg color.
Unchecking the “set color” box will make your background color transparent, allowing any layer(s) under that one to show through. This area utilizes a color-picker to allow you to easily pick colors for customizing. Click for more info
5) If you have a background image uploaded, you can delete the image entirely, or select “replace” to upload a different image. If there is no image uploaded, you will only see an option to upload an image. Clicking on “replace” or “upload” will open a ProPhoto upload window for you to add a new image. Click for more info
6) Information about the size of an image shows next to the preview of the uploaded background image to help you verify your image details. When the image is too large to preview at full size, a link is available to view the full size image.
7) A preview of any uploaded background image will show. Large background images will not be displayed full-size.
"Appearance" > "P3 Customize" > "Bio" > "Background"
Your ProPhoto Bio Area has two background options: Main and Inner backgrounds. Your main background is the ‘deepest’ background layer and the inner background layer appears on top of the main background. The inner background layer is provided to insert images like the page turn effect seen here:

The main background is a strip of grey gradient tiled horizontally, while the inner background (shown in red) is the page turn image positioned in the upper right.
Both image types are able to span the full width of the site, and can even be tiled to your preference. Using both background images can be used to create some flashy design effects.
General background area instructions:
There are many areas of your blog that allow you to modify their background colors and/or background images. ProPhoto’s interface makes fine-tuning these options a cinch. If the background area already has an image uploaded, you will see these options:

1) There are two general ways for a background image to be displayed, tiled or not tiled. A tiled image can be repeated horizontally, vertically, or both.

Tiled background images are nice because a small image can cover a large background area, keeping load times low. Images that you want to tile over a background should be created especially for tiling or they will probably have a visible seam every time the image repeats. Here is a tutorial on creating a seamless background image: Repeating Seamless Background Image Tutorial
2) When displaying a background image, you can determine where that the image will be shown.

Let’s say you are adding a background image to your blog’s outer background area. Choosing “top center” for an image that is being tiled vertically will repeat your image vertically as a strip down the center of your blog’s background.
3) Tell your background whether or not to scroll vertically with your blog content. An image that is not tiled and positioned “top center” can be set to “stay fixed in place” so that the background image will always stay at the top of the browser, even when visitors scroll down your blog content. (This option is only relevant for your blog’s outer background).

Fixed: When scrolled to bottom of blog, the outer background image stays in place.
You can see a live example of this here: Elegant Design
4) Set color of a background area. Background colors are always displayed behind any background image applied to the same element. If you set your background image to “tiled”, you won’t see your background color at all. If your image isn’t tiled, your background color will be visible beyond the edges of the background image. You can see this effect in the screenshot below, where a large background image was uploaded and set to “tile only horizontally”, “top center” and “fixed”.

The green box shows the background image. Outside of that, you are seeing the bg color.
Unchecking the “set color” box will make your background color transparent, allowing any layer(s) under that one to show through. This area utilizes a color-picker to allow you to easily pick colors for customizing. Click for more info
5) If you have a background image uploaded, you can delete the image entirely, or select “replace” to upload a different image. If there is no image uploaded, you will only see an option to upload an image. Clicking on “replace” or “upload” will open a ProPhoto upload window for you to add a new image. Click for more info
6) Information about the size of an image shows next to the preview of the uploaded background image to help you verify your image details. When the image is too large to preview at full size, a link is available to view the full size image.
7) A preview of any uploaded background image will show. Large background images will not be displayed full-size.
