Have you tried Ultimate Mapchooser? Link: https://forums.alliedmods.net/showthread.php?t=134190
It allows voting based on X number of maps from a pool that you specify.
For example, I use it to show this to players near the end of the match on my TF2 server:
2 random Capture the Flag maps (from a pool of around 10 that I specify in the config)
2 random Control Point maps (from a pool of around 30 in the config)
3 random King of the Hill maps (etc.)
1 random Halloween map
1 random Payload map
1 random Prophunt map, but only if there are at least 4 players in the game
1 random Death Run map, but only if there are at least 4 players in the game
1 random map that only shows 'Random Map' and if chosen will pick from a list of 50 maps in the config
It's not simple to configure but you'll like the customization capability.
I hope this helps!