Many companies use this software for editing photos.
I use this for our company work and this works perfectly for image editing process.
GIMP - GIMP is a multiplatform photo manipulation tool.
CollageIt - CollageIt is an easy-to-use and automatic collage maker, which makes photo collage automatically.
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
PhotoSpills - Easy to use PC collage software with unlimited design possibilities.
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
Collagerator - Create amazing photo collages in few mouse clicks. Ready for download for Mac OS X and Windows.