I love Dungeons and Dragons commissions. The world is so rich, there are so many playbooks, and unlike many visual RPGs such as Guild Wars or World of Warcraft, I'm designing a character from the ground up.
Recently I worked on a commission for a client I've worked with several times in the past. This time, he wanted a representation of his Tiefling Paladin, Ria (there's a long back story, but it's not mine to tell :) ) Being a tiefling, they have horns and a tail, and often times coloured skin that's not quite of this world. The skin and hair colour was very fixed in the client's mind and he provided some artwork as a reference, as with the symbol of Lathander, her God/ religion.
I always start with a couple of thumbnail sketches. In this case it was 4, but because I plan on reusing the poses I'll only show the one that we settled on. At this point they are really rough, the armour was combined from some different thumbnails, and the background was from a different sketch. You may be able to see some of my redlines from the pencil sketch this started from.
Unless the client says to go full fantasy, I try and keep the armour relatively realistic - that being said it is fantasy! I mix and match things from European 15th-16th century
If you want your own character commissioned, go to my commission page to see my pricing and some previous examples