I managed to figure out the "blue" thumbnails problem in 29. The only remaining moderate severity bugs are that Google Maps (the new one) still doesn't work properly, though old Google Maps does, and neither does audio or video-plus-audio in getUserMedia. The Google Maps problem seems related to canvas issues -- it does work, albeit glacially slowly, in 24, as do these animated canvas demos which don't work in 29 (only one frame is shown). I may still make a release regardless since we still need to test the widget changes against 10.5. While the webcam issue does not need to be solved before the launch of 31.0, the canvas problem does.
Unfortunately, PowerPC Linux users, it does not look like there's going to be a Firefox 29 for you or any of the *BSDs because of bug 961488. I can certainly look at it but it's going to be a while before I do. If you have the ability, please help debug what's going on -- keeping TenFourFox up, plus my day job and a Master's degree, has me very strapped for free cycles lately.