On the distance where it stops rendering totally try magpie's idea at end of this thread
http://www.twcenter.net/forums/showthread.php?t=427115
or have a talk to him and see if he got any further....
(think the blank bits on battle editor are the bits that show black in my campaign map example in that thread)
higher definition textures further out - not sure descr_geography if anywhere
tree distance (assume you're using the highest preference settings in which case tall_vegetation sprites already go to 'infinity')
IWTE does a convert vegetation.db to text and back again - either with that or hex editor you could try experimenting with this bit:
P.S. I think your computer might explode
