If you have an old laptop lying around that nobody wants, you can use it to make a WiFi-enabled LCD photo frame for around $80. Stripping the plastic housing from the notebook's LCD panel, this PopSci guy added a WiFi card, and ordered a custom frame that fit perfectly around the bare LCD.
Then he loaded the notebook with Slikr, a freeware screensaver that shows an updated slideshow from any Flickr account. Now the guy's mom can see whatever pictures he's loaded on Flickr, updated continously. It's even cheaper if your old notebook has its own built-in WiFi card. Doesn't look too difficult to build, either.
The DIY Digital Photo Frame [Popular Science]