There has been countless threads and posts about either the Europe map or in form of what makes a good map, a strategic map. I advise to read. Just to keep it short and leave the forum search function for you to discover as well the Warlight map creating Wiki page! So you settled from 3v3

Now think about particual map features:
- Balanced/unbalanced
- How many territories?
- Bonus size/territory ration
- Cluster bonuses
- Shape of map
- Bottlenecks, strangle-points, ships?
- How territories are connected. Distances from one point to other!

Illustrative: What period of map? Country-region-administration or what? If you are artful then add rivers-mountains or other distinquisable features.

Think what type of game-play you want to produce with your map and partiucal settings it could suit with. Like distribution (any particual distribution mode), base army and inital income, cards etc.

You can make anything good in 3v3, just need to think it over before. Like take for example of Rome map the most popular 3v3. So many people play it with Random distribution with 1-2 territories? There is nothing wrong playing it like that, but generally too much luck is put of where one lands rather how he plays his outcome. So try to think and create map in accord with what game-play you have in mind and test it. I also encourage you to post in description settings you recommend for particual map, especially if you add unique manual distribution team modes!