This one with a heart with wings and the word Mom written inside reminds me a bit of a tattoo, but this pretty image could be used for lots of things.
This gift tag that says "Happy Mother's Day" on it could be used in a webpage, email or even printed out, trimmed and put on a real gift to your Mom on this holiday!
A large image that simply says "Happy Mother's Day" with a bouquet of beautiful old fashioned roses.
This clipart of a computer with a screen saying "I Love Mom" is perfect if she loves surfing the net (and really, who doesn't?)!