There are groups for film only, there are groups for night shots only....but there aren't any groups for photos on film taken at night. until now.
Allowed: Anything on any type of photographic film, as long as it is taken after sunset. Flash shots are allowed, but no-flash exposures are encouraged. Minor brightness/contrast, burning/dodging, white balance adjustments in photoshop are allowed, but you should be able to produce an analog print from your original negative/slide that matches your posted scan. i.e., any photoshopping has to be able to be reproduced in a darkroom. Use your best judgement.
Not Allowed: Anything taken with a digital camera, anything taken during the daytime, anything heavily manipulated.