Alright fellas and fellerettes, your choices for photo editing software are plenty now a days if you're pullin' nothing but lint out of your pockets.
First, GIMP, this is a program you download and use it on your computer:
http://www.gimp.org/
Second, Splashup, this is a online photo editing software, similar:
http://www.splashup.com/
Third is Adobe Photoshop Express, another online one,
https://www.photoshop.com/express/landing.html
They don't offer all the features of Photoshop but will give you the tools you need to make a sig and do some edits on your truck.
Don't ask me how to use them or anything because I don't use them, I have Photoshop, but I figured I would share this with others so they can get creative. GIMP has some online resources for add-ons and tutorials and such though. I'm not sure on the other two.
Chuggs, maybe a sticky for this thread?