I just put out a single room map from my VTT map Crypt VTT 2 for free. Already tested it here in roll20 and it looks great. The maps size is 13 x 19 units (full map is 45 x 45). Check it out.
<a href="http://rpg.drivethrustuff.com/product/110446/Crypt-VTT-2-free-test-room" rel="nofollow">http://rpg.drivethrustuff.com/product/110446/Crypt-VTT-2-free-test-room</a>
<a href="http://rpg.drivethrustuff.com/product/110259/Crypt-VTT" rel="nofollow">http://rpg.drivethrustuff.com/product/110259/Crypt-VTT</a> <--- Is also free.
Thanks, and have fun.