I suggest you look at the Ryandor forums which is an excellent resource for creating maps.
The map sizes are hardcoded into client.exe, so you would have to hack your client to support your 100 x 100 map size.
Utility support for non standard map sizes is really patchy - you would need to recompile WorldForge, do some tricks with Dragon, and accept that UOAutoMap won't work any more. etc.
It's a lot easier to simply create / edit map0 but only detail a small part of it for your tests.
http://www.ryandor.com/forum/