It's actually not that bad for a first vector (I remember mine... uuuugh... lol). Though I have to say his hair looks the weirdest for me =/ I know that the double/second/copy strands are just shadowing, but due to the darkness of the shadows it really makes it look like hair and throws it off a bit for me.
Also it might just be me (I'm not good with word coordination in the first place) but the Red wording and the white below feel a tad out of place. I like the City Lights words and how you incorporated them into the wallpaper, very cool and thoughtful. I admire you for your buildings and their windows. For ages I've been too scared to vector actual buildings XD but you made it very simple and matching which is pretty cool. Though some windows look a tad jagged (but that might be my screen or something)
Overall I personally like the wallpaper, though I'd have preferred to see it in a larger size =p either way good job on ya first vector and nice wallpaper ^-^