1.5 out of 5 stars.

It would be better if they were cropped a bit more attentively and the white edges were removed. These could be nice but I keep seeing the messy edges and that just won't do. I don't even want to download them to check the hotspots while they look this messy.
And I just realized it was your first set. Don't be discouraged, it is a good concept, though I'm not sure what to make of the loading and help. You just should clean up the images a bit and resubmit them then I am sure they will be much better.

2.5 out of 5 stars.

No, I don't know how to change the workspace color in the editor.
You may want to ask Vlasta as he created the software.
Alternately you could post the question in the forum in the software section.
Please let me know if you find an answer.

I use layers sometimes to achieve the same results. Create a black background layer and place it below the image you are going to crop. Makes it easier to see the whites and colors of the image just like changing the workspace color would do.

Hope this will help..

*Remember to check your hotspots as that is crucial to the cursor functionality.