First off, on the subject of Tk, I highly recommend "Mastering Perl Tk" (the O'Reilly Emu Book) for a reference on all things Tk. It is very easy to understand (more so than most computer books) and it includes some features of Tk that you probably aren't going to pick up easily from reading CPAN.

I haven't done too much with images in Tk, yet, but I have added images to a Canvas using Tk::Photo.

http://search.cpan.org/~ni-s/Tk-804.025_beta8/pod/Photo.pod

Apparently, you can also use Tk::Bitmap to add icons to Labels (and I presume buttons as well). Out of respect for the author's work, I won't copy the examples I have from the Emu book.

bgstipple is apparently for drawing patterns, not graphics, so I would avoid trying to use that if there are files you would like to display.