I'd say that depending on how much more content is in the demo I wouldn't need a gallery myself, as long as you can save at states of undress. For later in game development sure.
I can't say that file size for dowloads matters too much. Quick dowloads are nicer to have to get to play quickly. If a demo takes a long while to download, but has little playtime that might put people off though.
As for the question about resolution I can't answer that I'm afraid.
I am very much looking forward to new development on this game. Thank you so much for keeping at it.