well, put them in 768*768 because there might be some details or junk things we can't see in 600*600...
well, I can see that lots of things are clearer now...but some logos are still a bit too big (H, W or both)...
and now your work is clearer, we can see that you don't use a good technique for the making, what you have to do is to put a layer template on Multiply at the very top and at the bottom the rest (logos, color...) as Normal: each logo will take the form of the template...
I can see that BPU logo seems like pastic bag...
difference between bmp and png: png is lighter than BMP, png can support transparency...
for Kit viewer check on kitmakers ressource thread (file .o) and here is maybe
OEdit for you
program: you should take The GIMP, it's free, light and very good...
that's what I use