Thank you so much for your feedback, everybody! I really like most of them as ideas, though I have to admit that 12 doesn't really say isolation to me and 7 and 9 have some silhouette problems. Right now I'm drawing out 4, with 5 and 11 in my back pocket if I don't like how it comes out. Sometimes you just have to draw something out before knowing if it's going to work!
One thing that I learned through this process is that although "solitude" (time alone to concentrate) can be positive, "isolation" (lack of connection) has a negative connotation for me. Spending the last two months without seeing another face up close just hammered that in even more. So the "lone wolf" for me is really a character who is discovering his need for others, hopefully with a bit of humor. And 4 is the darkest of the thumbnails, so I really hope I can get the humor across in that one!