To see me talk to the character, check out the interview blogfest entry, which was fun and a shortened set of answers. I have used Harley's character worksheet, with most questions answered except where irrelevant to him. I will post answers from that down below.
---Interview can be found HERE
He is blonde and I've done two different images using the same web site. I like the lighter blonde coloring (even though he's more of a dirty blonde) and both are bit younger looking, though he only lived in real life to the age of 18. Used to dye his hair a lot too, temporary, mostly unnatural colors. Slim but never really worked out. But for now, some possible images for him (ignore skin colors cause I don't have that figured out cause it doesn't matter in the book and the avatars don't have many options for changing it).
Eye Color: Green
Originally from Southern California, now lives in Detroit.
Nickname: Doesn't have any nicknames. Does not like when people call him Luke.
Before Death: Hadn't graduated from high school yet with a tendency to skip classes and party late at night. Lived at home with his parents. Gay and he slept around a bit without really dating. Kept to his small circles of people and to himself. Didn't do drugs except a few trial ones, but did drink often. Didn't believe in God.
His parents - Mom was really nice and tried her best. Dad was more of a jerk, would get physical sometimes with him. Mom was religious and tried to get him to go to church with her but usually Lucas wouldn't go.
How he died: Wrong place at wrong time. Was walking home and was shot in a drive-by that wasn't actually aiming for him.
After Death: Demon. He's a very low level though, known as a runner (which is a type of messenger). Still gay but he doesn't let the demons he is stuck with know, because it's the only little bit of fun he has for awhile in keeping it a secret. He
Friends/Co-Demons - Mara is the token female, in some ways. She's a bit protective and puts up with his complaints with more patience. Nicor, goes by Nic, is the leader and a straight male. He tires of Lucas but partly because he has to give up his couch so that Lucas has a place to stay. Then Andras, who liked to have fun, and sometimes hits on Lucas just because he can. Sam was his friend in California, and he helped him transition after death to get him on the train to Detroit.
Lucas feels a bit lost at this point in the novel, in the beginning, like he missed something. Doesn't know if the emptiness is foreer or if something will change it.
That is Lucas. Or at least, him in chapter 3 of the novel.