custom background view shows cropped image and not original upload

[obvio]

trying to upload a very tall image to the custom background area (for example 100*1100px width*height) works but the image that is then shown in the view-pane is the cropped/thumbnail version of the upload and not the original image the user added.

it is possible a site would have a repeat-x on a really tall image.

I can reproduce this on current trunk. For example, this is the preview pane of an image sized 150x1000: ​http://cl.ly/image/32051X0f020S

Agreed. Even this is the intended behavior I found it confusing. It would be better to display the original image instead of its thumbnail.

Also found that saving a custom background from the theme customizer produces unexpected output on the Custom Background screen.

Steps to reproduce:

1. Upload a custom background from Appearance > Background and save. Everything looks as expected (attachment:custom-background.png​, top).
2. Open the theme customizer (Appearance > Themes > Customize), edit anything and save.
3. Return to Appearance > Background. Now the original image is displayed instead of its thumbnail and the preview pane is very tall (attachment:custom-background.png​, bottom).

This is caused by the update() callback from WP_Customize_Background_Image_Settings class which removes the thumbnail theme mod.

attachment:14979.diff​ uses the original image instead of its thumbnail and sets the height of the preview pane properly when a custom background is set. Also adds control over the background size as shown in attachment:14979.png​.

Related: ticket:22058.

@cdog Great! I was thinking this was missing. Could you also add -IE8 support also? ​http://css-tricks.com/perfect-full-page-background-image/
​http://msdn.microsoft.com/en-us/library/ms532920(v=vs.85).aspx

Thanks