Those look really great and now you have given me more ideas for new projects! Thanks!
I have had really good results using TransTint dyes on my projects. They come in about 18 colors and you can mix colors to get others. The dye also allows the grain to show through.
Welcome. Also from OKC here. GIMP is a good program, I would also suggest downloading Inkscape (also a free program). I use GIMP when I want to convert a picture into a scrollable pattern, and Inkscape I primarily use to create patterns from scratch. Have fun!