Movie and still specs are: up to 4096x2048pixels
(unless recently changed...)
subject to hardware limitations

AIC is best 'all round' quicktime codec for movies
Also supported:
PhotoJPEG
DV PAL/NTSC
Animation Codec (alpha transparency)
Quartz

Stills:
JPEG
PNG (alpha transparency)
TIFF (alpha transparency)

Always test a sample movie / still before rendering out 1000's of files!!!

There are conversion tools built in to catalyst - However, its always best to get files in the correct format at time of renering....

Simon