He looks so cozy in the little sweater! I'd not want to put my bare butt on my porcelain tile floors, I can tell you! I don't blame him one bit!
With so little cushioning between his ribs and those big buttons, I wonder if he might get uncomfortable if he tries to lie down on that side? Maybe a bit of Velcro would be less of an irritant should he decide he wants to lie on this right side? Just a thought. I'm sort of like the princess and the pea, so I think of those things.
When my granddaughter had a chihuahua, we made her two outfits: Pajamas & the most adorable little dress. It was so much fun. And she looked so cute in them.