I have been making my own decals for about 6 months now. I use an ALPs printer as it will print white, and the inks are waterproof. I print on clear decal paper and after the decal is applied I wait a couple of days for it to really get set and spay some clear over it to fuel proof it.

All my decals are made using Corel Draw as it is a vector program. Raster images will not print out as sharp and look pretty bad on the model if you try to enlarge or shrink them.
If you get good fresh decal paper, it will mold itself around panel lines and rivets very well and will look like paint when finished.
Hans