Steve,
Great suggestions (negative filter + color swap).
PSP is one of the apps I have used, and I find it to be simple to use and powerful.
Used Corel Draw back in the 1990's, and dabbled a bit with Photo Shop (too many $$$ for me!).
Got very use to Corel Draw, and used it quite exclusively from 1995 to 2000 or so.
Went to PSP by a suggestion from a close contact, and really liked it!
(Corel Draw version I had was becoming too antiquated for use with newer image file formats).
Scott