Questions about example sentences with, and the definition and usage of "Skinner"

A: × I wish they could make me look skinner in the picture haha
✓ I wish they could make me look skinnier in the picture haha

This is only for very informal conversations, like among friends, of course :)

A: × ‎My skinner is my favorite mountain!
✓ ‎Mt. skinner is my favorite mountain!

If the listener is looking at the picture from the grand canyon, or if they know which picture you are referring to, "the picture" is correct.

If they have not seen the picture, and this is your first time talking about it, use "a" instead.

Also, I'm not sure if you meant "Mt. skinner"? I don't understand "My skinner"