UK's Mobile Fun has listed two case lines - Trident's Aegis and Kraken - and claims they will be fitting the upcoming Galaxy S5. Those case prereleases are usually based on an intricate combination of rumors and guesswork, but often on schematics that part suppliers leak to case makers, and even official dimensions forwarded by the phone manufacturer before the actual unveiling.
In any case, pun not intended, take a gander at the case collection that Mobile Fun claims is destined to wrap the Galaxy S5 snugly. If we can gauge anything from these, it's that the camera unit might have its typical place in the upper middle of the phone's back, while the volume rocker is set on the right, and the power/lock key is on the usual left.
The case maker also notes that its products have "cutouts for the flash, camera, loud speaker, microphone and noise-cancelling microphone." Cutout for a fingerprint reader is mentioned nowhere, though, so if the cases are indeed designed after the S5, such a scanner either won't be present in the phone, or it might be embedded in the touchscreen itself indeed.