Texture paint uses one image for different objects Blender's texture painting is making me crazy right now.
I'm working with cycles and I've defined two different images in the node editor. One for each of my eyes in the own node editor.

Still... I can't paint on the different images. If I go into texture painting, I can only choose a picture in the slots window, and it displays it on both of the eyes! They shouldn't have any connection at all - different objects, different node - still I can't work on them separately. 

I'm not used to this new Slots settings, and guess something is working wrong there. But I don't really know how to fix the problem.
You were close. Instead of changing painting mode, you need to specify on what image you want to paint, selecting the canvas image in slots panel.



It's handy if you want to clone to specific image from multiple different UVs and images.