How do you know you're not breaking some other application or service when you take the .254 address?
Because I setup the network. I usually use .1 for gateways, .2-.10 for devices like managed switches or monitored UPSes (basically, infrastructure stuff), .11-.30 for network resources (servers, printers, etc.), .31-.99 for access control/cameras/environmental monitoring devices, .100-.200 for DHCP pool, .201-.254 is typically unassigned. (this is assuming a 'simple' /24 network).
If I did not setup the network, then I would check first with whomever had allocated IP space (which, frequently, is nobody).
Use the correct one and if the camera's shouldn't be reachable outside the subnet don't use any.
The majority of my career has been with some form of startup company, and/or working with pre-release products from other companies. I have come across countless devices with buggy implementations that want values for gateway's, even if they have no need to communicate outside of the network. It is less common in 'production' stuff, but as I alluded to in my earlier post, sometimes the software 'wants' a value there.