Right. I can only post about my experiences and all evidence is completely anecdotal.
Current map list:
de_dust2
de_inferno
de_nuke32
de_dust
de_train32
de_westwood
cs_assault_shadow
de_dust2002
Issues we have, difficulty getting the server started from empty (we tend to use de_dust2, attract a few people then when the map changes they leave...)
Popular maps that in my experience attract players once you have the critical 10-12 players needed to have a healthy server. I would definately keep:
de_dust2
de_inferno
de_nuke32
de_dust
de_westwood
Maps that seem to have a net negative on player numbers and I would suggest removing:
de_train32
cs_assault_shadow
de_dust2002
Suggestion, add a few 'starter' maps for the admins to switch to as typically its admin vs admin until enough players are attracted (Maybe until 10 players?). Specifically these maps would not be map of the default map list nor part of the automatic map cycle. I'd suggest:
fy_snow
aim_map
awp_india
fy_pool_day
(Even though I hate awp maps, some people dont)
Once per month cycle in a 'flavour' map which is swapped out on a monthly basis and can be part of the defualt map list and vote options (lets player power decide, if enough people want it - they play it). Flavour maps (only one on at a time):
de_cbbl
cs_estate
cs_italy
de_dust2_2006
de_aztec
de_train32
cs_assault_shadow
de_dust2002
If any map is proving horribly unpopular then it could be cycled out from imediately and removed from the list. Notice the removed current maps would still get a chance to shine in the flavor map list and if they prove overwhelmingly popular a map can be promoted to the full list. I think this gives us a stable base, some experimentation for variety and a way to 'try before we buy' for certain maps. Thoughts?