The correct expression is 'What else?' For example: What's in the fridge? There's cheese, eggs, chicken... What else? Umm, just some tomatoes. If you have heard anyone say 'What more?' in this context, they are wrong. Spanish speakers often try to translate 'Que más?' literally, but this is incorrect. It should be 'What else?' Note that we also have 'Who else?' 'Why else?' and 'Where else?'

"what more" alone is incorrect. In some structures we can say "what more" for example "WHat more could you want in life?"

I cant think of a context for "what more?"

*What is the difference between the two? There is little difference. Do you have a context in mind?