The next video I make will be about using Skins in Spine. I won't be able to get to it before Monday I'm afraid. For now take a look at the goblin example.

Step by step.

1. Create a skin by clicking the Skins node and adding a new one in the properties.
2. Select a slot and create a skin attachment.
3. Drag your image on to that attachment (looks like a puzzle piece)
4. Create another skin by doing what you did in step 1.
5. Set the new skin set visible by clicking the visibility dot next to it.
6. Drag a new image onto the attachment you created in step 2.

You can now switch between the images by clicking the visibility dot next to either of the skins.

Hope it helps.