Check this thread for image making program linkshttp://developer.thegamecreators.com/?m=forum_view&t=29771&b=4
Anyway, my addage is "if you cant draw it, sample it!"
Im going to make some tree graphics and I find it really difficult to draw realistic branches, so I looked for reference on Google. I found the best source was pictures of bonzai trees, so maybe use some photos of the japanese tree in a pot, they look really stylised. Remember as well, any part of the image you want to be transparent set the coulour of that pixel to 0,0,0 RGB!
Good luck!
GIve me more power!