lets see... map making handbook i think has the size restrictions... yep, here it is!
1. SMALL MAP: WIDTH up to 630 px; HEIGHT 600 px
2. LARGE MAP: WIDTH up to 840 px ; HEIGHT 800 px.
3. SIZE DIFFERENTIAL: A large map must be noticably larger than their small map; 9% larger is required but 33.3% (1/3rd) is recommended.
4. NOTE: Mapmakers are encouraged to make their large maps smaller than the maximum size limits when possible to eliminate scrolling to attack/read the sidebar info.
so yea, small map width 630, and height 600, with large height width 800, and height 800. You can change those around a bit, but those are the maximum map sizes. So for large you could have 800x100, and for small you could have 600x400, but the others are the max
I suggest you read the rest of the handbook, theres some good stuff in there
http://www.conquerclub.com/forum/viewtopic.php?f=10&t=40463maybe look at map tools also if you need to know programs and such, it can be a big help