Yep. Baobabs are a good example. I saw one on the salt flats of Botswana that was definitely over 20' wide. just assumed that these were standard deciduous trees and thought the trunks were a bit huge. If you want them to be unusually proportioned for whatever reasons them I'm definitely not going to stop you.

I like the colour scheme - it's very clear.

I realise you are using Gimp - I was just wondering whether you were going to drop the image into a virtual tabletop program when you play a game on it?