paintbrush question

hey i downloaded paintbrush because i wanted a simple app similar to ms paint..

i want to copy a bunch of pictures i have onto a blank paint screen to make a collage.. but it won't seem to let me..

does anyone know how i can do this or know of a better freeware app to use?

Gimp perhaps?
or http://www.mac-forums.com/forums/showthread.php?t=104945