You can get more trees here:
http://rpgmapshare.com/?q=search/gal...ields%3Atitles

If you want to turn them to autumn colours you can colour shift them in a number of different programs. Are you using maptool to create the map - and then print it out? That seems like a slightly long way round.

Also, more here:
http://www.dundjinni.com/forums/foru...=10840&KW=tree

And there's 9 pages of search results for 'tree' in there. I'm sure you'll find some trees there you can use:
http://www.dundjinni.com/forums/sear...M=0&OB=1&SPN=2