There is no need to take a still image at the end of the first sequence. No matter the medium (dv, 8mm, 16mm, etc), use the last frame as the tracked element for the living room. If you were to use a different picture altogether from a different camera, it would have a distinct look+feel different than your original footage, and would stick out like a sore thumb. Just use the last frame and color correct to taste, that way the element wont change unnecessarily and 'break' the scene. as long as your markers are clean, its no chore to complete.
(video tutorial link) http://www.cmivfx.com/m/hp_style_cmivfx.mov
This is a link to a Digital Fusion tutorial depicting how the HP commercials were made, and demonstrates just how simple it actually is. DF is not necessary, as this trick can be done in any package (shake, combustion, et al).
The projection patterns in the fog dont have to necessarily be 'correct''. as long as there is very little fog in the room a little dry erase marker on the lens will produce a 'noise' to project through. it doesnt have to be believable, just constant.
my 2 cents :)