I've enjoyed this game all in all. And I love playing multi-player. But the maps get extremely repetitive in multi-player. I'm not saying you need to make more every couple of days, but mix it up a little bit!! Every time you change maps I have fun with them for a while. Then they get really old. I find myself missing the old maps, or anything different for that matter. Here is what I propose: Have one of your junior developers create a randomization method. Whenever anyone starts a multiplayer match, give them a 50% chance to start on one of the new maps of the month. The other 50% is a random map from every multiplayer map you have ever put out. Not only will this bring some much-needed variety, but most players have not seen many of the maps from the first year, and they would appreciate the opportunity to be able to play them.
I was getting ready to flame you when I started reading this... but actually it's a very good idea. What I would say is this (and your suggestion already address it): I'd like to see a little more variation within the selection of maps each month. Hallowe'en were the 1/1/1 maps, then were replaced by Whirlwind maps, and now we have WWE/NS maps. What I want to see is enough of a selection that no single deck is going to break face on every single MP map in a given month. As said in the OP - this needn't actually require any more work if you just add a few of the old maps into the mix; maybe reskin them if you want to keep them thematically linked.
We should note that there are no "Junior Developers" (at least as far as I i know) at BM - it's still a very small company.