This is by no means an exhaustive list... and I don't have photos, sorry... but here's a start!
SureFire L1 Evolution
Gen1: Body has four flats. Head is short and tapered. Lens is flat. Bezel is plain (NOT scalloped). Optic is NX05. Emitter is Luxeon low dome.
Gen2: Like gen1 but bezel is scalloped. I believe some of these came with the SureFire lanyard and attachment in the box. Somewhere along the way the box style changed from cardboard box with lid to cardboard one-piece box with top and bottom flats, internal plastic tray, and clear plastic window through which the L1 is visible.
Gen3: Like gen2 but emitter is Luxeon high dome. Note that optic is still NX05.
Gen4: Head switched to larger, KL4-like head with TIROS optic, domed lens, and Luxeon (III?) emitter. Body is still the four flats version. These seem to be relatively rare! Probably a short production run before switching to the newer, rounded body.
Gen5: Like gen4 but body is rounded (no flats).
Gen6: (shown at SHOT 2007) Body seems to be 25% shorter than gen5. Head seems to be a little shorter than gen5 head, with emitter switched to Cree XR-E and optic switched to something similar in appearance to a Fraen LP optic... it has a hole in the center that goes all the way through... one can look directly at the emitter dome through this hole.