Double Fine Adventure (codenamed Reds) is being steadily worked on, and art is being made and shown off for it all the time. If you're not a backer, you still have time to rectify that and become one so you can get access to the private backer forum and see the progress for yourself.
Or (or, even better, and) you can buy the Double Fine Adventure Lumberjack Print in pure Bagel style* for yourself for a mere $30.
- That would be the style of Nathan "Bagel" Stapley, the lead artist of Double Fine Adventure
SurplusGamer
It's not concept art, really. Just pre-concept art used to test the technical side. No announced in-game lumberjacks.
Yeeeah, saw that afterwards. I knew the original lumberjack I saw was concept, thought this was real concept art. Either way, a lumberjack puzzle sounds like a good idea.