Looking in on this very late but to echo what has been said.

No grid makes for a good VTT map.

JPG makes for a quick easy transfer.

PNG makes for nice icons/tokens

One thing is to offer the tokens at a lower resolution also. Loading up a map then tossing 10 tokens on it plus the Player Icons, etc can really slow down transfer times - especially over DSL speed connections

The above examples would be fine for battle maps in a VTT if they did not have the grid on them.

BOB