Mikey,
The old ease vs flexibility tradeoff. If you want to get really, really smart, you do as Mikey says, but you also (a) allow optional addition of a path as part of the filename, and (b) a file extention as part of the filename. (c) You use these optional additions instead of the defaults when they are provided. This provided the best of both worlds; ease and flexibility (flexibility in the sense that you can include different types of images, and they can be located in different folders).
Cheers,
Steve Lewy
Solutions Developer
steve@lewycomputing.com.au