This page should help from when I did a hunt a while back
https://sites.google.com/site/15mmfantasy/15mmfantasyranges
Now I never got round to buying into any, but I always thought this guys work
https://www.microworldgames.com
Was some of the most impressive and had the most detailed/carefully designed models. A fair few have some very iffy/soft details and designs in tehir 15mm stuff, however as many are small time pet projects they also tend to have pretty poor photos (really poor in some cases) which can seriously hamper the ability to show off the quality of what they'd made
Also the Ral Patha stuff is being remade and re-released and they've had several recent kickstarters (one just recently ended) (although my impression of the range is that its a bit hit and miss- some stuff looks great, some looks rubbishy and some is very "retro"
https://www.ralpartha.com