Just my opinion on the pic size:
Physical size:
The bigger the better
File size:
100kbs is a HUGE file to open on a dial up connection & that's still what most surfers use...
With a picture of 600px (long side) you can easily optimize well below 50kbs and get a good quality picture.
Why waste the b/w & turn away so many surfers?
Now that most wm's are using broadband connections this problem has multiplied beyond belief
