The problem, too frequently, involves file size.
I found a background image I really like (or at least I think it would work OK) - but when I resized it to the upload specs detailed in customizing your template, it said the file was too big!Blogger limits background images, as supported by the Template Designer, to 300K.
You have to be aware of various details, of any image, photo, or picture.
- Colour depth.
- Physical size.
- Compression type / file format.
Physical image size (height x width) x Resolution yields number of pixels in an image. Colour depth x Physical size x Resolution yields the actual file size, as a bitmap (".bmp" and similar file types).
Reduce image content, to reduce file size.
Every non bitmap file type uses some type of compression, to make file size smaller than bitmap - and will generally produce a smaller file. The ".bmp" file type is the best known bitmap.
With some formats, if you improperly resize some images to be "smaller", the physical file size will increase.
To make a background image file smaller, reduce colour depth and resolution.
You need an image processing program that will make files smaller, when you resize the image.
If you have an image that you like, try reducing the colour depth and resolution. That is best, to make background images most useful.
A background image should only be semi visible.
If you're displaying a foreground image, in the Blogger lightbox or similar full size display, you would want full colour depth and resolution, to make the image content most visible.
If you're displaying a background image in a blog, you want the image to be - - background. Colour depth and resolution, when decreased, makes an image work, as a background.
If you use an image editor that properly stores your changes as reduced file size, it also makes the file size much smaller - and gives you a better chance of staying under 300K file size.
Use the Template Designer, to install any suitable background image.
When you have your favourite photo or picture properly prepared, use the Template Designer "Background" page, to add it to your blog. Select "Upload image" from the "Select background image" wizard, and follow instructions.