LXer has a link to this digital photo frame kit running Damn Small Linux. It includes WIFI, so you can probably SSH into you photo frame.
GOSHEN, Ind. – RedPost inc., an Indiana-based tech startup, today announced the launch of RedPost/Kit, a do-it-yourself digital photo frame kit that comes with everything you need to get up and running.
SSH is not enabled by default (samba is) but it’s included with the default DSL installation and just has to be set to startup at boot.
More documentation on our modifications to DSL:
http://www.theredpost.com/kit/doc/