Wow, why is it that ever since i stopped remaking MY coldharbour RP that everyone else feels they want to make one? ive seen about 4-5 people make an RP set in coldharbour since i last remade mine.
but nothing bad with that, i will say that if done correctly Coldharbour IS a very good place to set a roleplay, as i proved when i made mine about a year or so ago. Its very easy to get yourself orientated because it is basically a twisted reflection of Nirn and so if set in coldharbour's cyrodiil or morrowind any player would easy become familiar with the surroundings just with some horrific artistic liscence.
if you do end up making it in coldharbour id be more than willing to give any info we drudged and dreamed up in the creation of mine, which will give u a good starting point as to where to build upon.
just remember that it is described in Lore as being very eery and quiet, and that the sky is flames. it is filled with charnel houses (building full of corpses like a corpse warehouse) so would make for a good horror setting, and slave pens filled with mortals from nirn. and dont forget the vampires