Been playing this for a few days now ever since it showed up on GOG Connect, on an old ASUS 1215n with an Atom/ION combo... and Nvidia Optimus apparently wasn't detecting the game...
Played it for hours with a grossly pixelated/compressed splash screen and start menu, a few missing backdrops and (of course) the OP's problem of not being able to view fullscreen pics in the thumbnail gallery.
Adding the .exe to Nvidia's contral panel and forcing it to run on the GPU completely fixed everything for me. Splash screen looks great, the few backdrops that were black (Campus, Beach etc) now show up, and the thumbnail gallery now works flawlessly and I can view images full-screen. Game is faaar zippier too.
Long story short, my Intel Atom was doing a piss-poor job of rendering the game apparently. I've no idea if there's a fix for it but someone here might. But if you've got a dGPU just force it to run the game.
Hope this helps