hi,
I want to build a wall clock sort of like this:

http://www.gizmodo.com/gadgets/gadgets/pong-wall-clock-coolness-to-the-max-139434.php

not necessarily the PONG motif, but some other animated graphic (although I might copy pong to start)

I'm going to use an old LCD monitor, and put it in an old wooden picture frame.

Any suggestions as to what hardware (motherboard, graphics card) to use, that would fit in back of the frame?

MiniITX stuff would probably be the proverbial bees knees.

I dont know if they still make the 500mhz version, maybe you can find a used one?

One of those tiny little gum-stick Linux machines may do the trick, although the name of them escapes me for the moment...

gumstix was my first idea, but I don't believe there are any graphics card modules. anything smaller than a mini-itx, with integrated graphics card, at a reasonable price?

How about hacking a Playstation or something? They're small enough, and you can pick them up for next to nothing...

Gumstix can drive LCD displays:

http://www.gumstix.org/tikiwiki/tiki-index.php?page=Display