I dont think warmongering is bound to a leader. Some might be better suited for it, but it is more a question of how the player set his priorities. Focus on building units and making war. Make you a checklist perhaps. Follow the objectives, leaving everything, that does not help those objectives out. Something like:
-Explore, find you close neighbours.
-Choose one (maybe the nearest, or perhaps the one having the best land, or...) and kill him as soon as you can. Best with a early rush.
-Recover your economy, modernize your army.
- Go for the next victim
Note theat there is nothing in the checklist about building Wonders or getting religions. If you consider doing this, ask you self: How exactly does this one help me achieving the next objective (e.g. killing the next Civ faster) ? If you have no answer, just skip it.
Take a look at Sisiutil's guide for a early rush - in case you dont know it yet. Rush someone in your next game. On Noble it is easily possible to rush more than one in the same game - if you have enought neighbours, that is.
http://forums.civfanatics.com/showthread.php?t=244075
As for maps:
Dont choose to big size. On huge the starting plots might be to far apart to rush. If playing big map, try slower speed (epic perhaps). But best play Standard size, and maybe stick 8 or 9 (instead of the default 7) civs in it. A Pangaea will guarantee you easy access to your victims. If you want to practice naval invasion as well, try Hemispheres with 2 continents.
Leader is not that important. Still...
Perhaps You could try Ragnar and the Vikings. Aggressive will give you units with Combat 1, thus unlocking many other promotions, while Financial will help you with paying your soldiers salaries, upkeep and research. The UU is not bad as well. Replaces maceman - so it will not be used in the early rush. But it will give you additional motivation to go to war again later