It's easy to use ImageMagick to manipulate images on the server.
If you have it installed on your system, the unix program "convert"
will convert virtually any format and geometry into any other, and
can perform image compositing, text and graphics, etc.
AOLserver handles file uploads from browsers quite nicely, it will
create a temporary file for you, so you can just write your tcl script to copy the file to some archive directory, then execute "convert", and keep a pointer to the filename in your db.
There is some debate over whether to keep image files in the
database, or to keep them in the filesystem and just keep names in the database. I recommend keeping the image files in the filesystem in almost all cases.
