Not that I know of and that's mainly due to a software limitation more than hardware.
You could put a higher resolution screen in, but the 3DS' GPU will still display images at it's default resolution (800x240 is the default resolution. If you put in a higher resolution screen, it'll still only display 800x240 images) as that is hardcoded into the device.
The camera and SD slot are most likely integrity checked against a whitelist of component IDs. If you put in a non-3DS part, there's a very high chance it flat out will not work at all because of the hardware check or at best, won't work properly (it'll behave like the original part, even though it's upgraded).