I am trying to make a football texture in gimp. Is there any way to make the small round bumps in gimp?

Small round bumps can be just drawn, copied, than use it as brush to reproduce lots of bumps. You can use photo of the bump texture; layer and overlay. I did look at some football photo on the web and found that bumps are 3D and depending on the light angle it cast totally different shadows you know.

Blender Voronoi texture can simulate football bump. So I did quick study. I had problem adjusting Voronoi to give me constant bump. That is, bumps are different size and different intensity. Football bumps are more uniform in size and height. But you can always copy Voronoi image from Blender and “fix it up” with Gimp I think.