ALL ASSETS need to be on PNG format and with a transparent background. Make sure not to have a lot of empty space in the png (thank me later).

You can also piggy back on the art of other artists (as long as you have their permission or their work is Creative Commons). Just search for images that are hand drawn and look for the ones that have the right perspective (you can always adjust it a bit on Photoshop). Then remove the background... et voila, your asset is ready.

And all this said, feel free to make completely different styles if you are the one curating the whole map!

Examples of different styles:

*PD: Topia will soon launch a marketplace for you to buy assets created by others