I noticed that there isn't alot of OC's in VM fiction though that probably is because Veronica is really likable as a character but sometimes I like to see things switched up with new characters to read about. You can pick out names and personalities for the OC's of course though I will set some points for you to start with. All are Lamb/OC and Veronica is with Logan.
1. Veronica has a twin sister that's coming back to Neptune. The twin must either have been taken with Lianne after she left or she was in boarding school/or living with an aunt away from Neptune so no one from Neptune has met her if she's been living with a relative her whole life. When she comes back to Neptune, there's a case of mistaken identity when Lamb arrests her, thinking she's Veronica. Takes place during Season 2 or Season 3 (basically when Veronica and the OC are 18)
THIS ONE IS MY FAVORITE!
2. Veronica has a 22 year old cousin who's never been to Neptune before. She's moving into the guest room in Keith and Veronica's apartment. What will happen when the citizens of Neptune begin to notice the new Mars in town? And what about a certain Sheriff? Takes place from Season 1.
3. Veronica has an older sister (not a twin) who's been away at college but is home just in time to help Veronica in her investigation of the bus crash. What happens when she and Lamb meet? Takes place from Season 2.