No I would have gone for GIMP. I believe its better than Photoshop (which is not free). I don't know enough about CC3 to comment, I only know Photoshop and Gimp. Having discussed software with other cartographers on the CG I know that each person has their different preferences. You need to find a programme that suits you and make it work for you. For me, that was always going to be a good-quality open-source programme, in hindsight, so I think I personally would have ended up with GIMP whatever I tried first.
in retrospect, after learning the ins and out of GIMP, would you still have gone that route? or would you have picked another software like photoshop or CC3?
When I was making these maps I used pre-made items. If you read through my WIP thread (link in post 1) I usually link to them. For comission work (ie if I'm making a map to sell, not just for myself) I would be much more careful; but in fact nowadays I make everything myself and have a very pared down map approach. I use lots of dunjinni objects and now I always very carefully reference every pre-made item I use and check it's open source or whatever; you can see my more recent work on dunjinni
For the all the items and such inside your maps, is there a free repository that you grabbed from, or are they all self created?