My friends and I have decided to make a cafe game. I am aware that this is not the most original idea, but we wanted to create something with the limited knowledge we have.
We have been trying to brainstorm the thumbnails and icons, so we could make sure we had enough funds. However, we don’t know what kind of thumbnail / icon we should do, like one that is drawn, a GFX, etc.
Any help is greatly appreciated!
In my opinion, You should do GFX, I think It’s better than drawn one.
To make it look professional, maybe try using GFX, however, for the logo, that should be 2D art, however for thumbnails, it’s more recommended a GFX is placed there, putting up 2D art, would not really be recommended unless it’s not a roleplay game and more of a competitive or adventure, type of game
Some people sitting down, maybe enjoying the food/drinks you have to offer? You could also have one of people working and making Drinks and Food. Hope this helps! 
Like what megapaul stated, make a GFX for the thumbnail and have a 2D icon. There are plenty of cafes that do this, and I’m pretty sure they wouldn’t mind you making a GFX with the same general and typical cafe art concept.
Would recommend the same thing as what megapaul said, and for what the GFXs could look like, try basing it off the name of the Cafe.