Boba Fett concept art by Joe Johnston and Ralph McQuarrie with a bonus picture of Jeremy Bulloch in the near-finalized costume.
Before Boba Fett was Boba Fett, Ralph and Joe were tasked with designing an “ultra” Stormtrooper that (I’m assuming) would have been part of an elite Imperial task force or some sort of special forces unit. Somewhere along development, it was decided that this elite Stormtrooper would instead be its own unique character, and thus, Boba Fett was born.
If I’m putting the evidence together correctly, the design for the costume was practically finalized when it was decided that the trooper would instead become Boba Fett. As a result, one of the suit’s early color schemes was entirely white to match with the original Stormtroopers. You can get a good idea of what that looked like via this action figure. Still, however, you can see that McQuarrie’s early sketches of the helmet (Images 2 and 3) draw heavily from the original Stormtrooper design before attempting to move away from it.
I’m sure these images have made their way around the internet more than enough times, but I’ve had these saved for a while so here they are. Besides, everybody loves the Fett.
All of these images (excluding the image of Bulloch in costume) were taken from The Dented Helmet forums. There are more images there along with the ones I’ve posted here, so check it out.