During my career I've always found myself to be more of a 2D generalist. But I find concept art to be one of my favorite areas to work. I love to sketch and I'm sure that's part of the reason I enjoy it so much. There's a lot of freedom and creativity involved in developing something new or spinning something that's already been rehashed a hundred times. Not to mention the fun of collaborating with other artists/writers to see how far something can be pushed. Creating new worlds is always a blast!
These were done in the early years of my career. Someday I'd love to get back to doing more illustration and concept work full time.