normal features for a website...
Castle status - done.
Seven Signs status - done
Rankings - hmmm... im waiting for a good design idea to fall from the sky
Raidbosses map - done
Dropcalculator - dunno what that is.. but ill find out
server status - done
online players count - done
Donation page (with administration page if possible) - when i figure out the item system i will
Teamsspeak/ventrilo server info/viewer (this is something that every decent server has) - easily replace chat i put in there i guess
for user CP:
change password - done
change email - done
password reminder
character stuck fixer - hmmm
and if you wanna go deep into that...
warehouse/Inventory management
recipebook viewer
craft calculator (based on what you have on inv and WH and why not ClanWH)
those are a couple of ideas that came up to my mind right now. as you can see easier you make it more ppl will like it. and since you plan to make a paid version. I think there are listed some options that should be in a paid product.
I know some of those can lead to potential security problems, but nothing that a skilled php coder can't handle, so I'm sure you can do it.
Droppo.-