Motley Crüe made out like bandits on its farewell tour by ripping off two famous rock 'n' roll photographers -- slapping their work on all sorts of merchandise ... according to the photogs.

The Crüe rode off into the sunset with the 2014-15 tour, and sold a bunch of gear with classic images of the band from its heyday in the '80s. Barry Levine and Neil Zlozower say they took those photos, and the band never got their permission use their pics.

In their lawsuit Levine and Zlozower say Motley Crüe hawked t-shirts, crop tops, stickers, vests, flags, patches ... and even babies onesies featuring their famous photos -- but they got bupkis out of the deal.