Since you have Photoshop…go to your preferences and set Photoshop as your default image editor in SketchUp.
Then find and edit the cheese texture and it should open in Photoshop directly. Then make the changes you want to it and make sure to merge the new layer(s) or flatten the image in Photoshop and then save it. It should then automatically update in SketchUp. Repeat the process as many times as needed.
