Reader LindsayJoy just received her Indiana Jones and the Lost Tomb LEGO set, complete with snakes, the Lost Ark, snakes, Marion, snakes, Indy, snakes (I hate snakes,) and a special piece we didn't notice the first time we saw the first production set photos: a piece with the hieroglyphic engravings of R2-D2 and C-3PO in the Well of Souls, just like in the movie. [Update: actually, not like in the movie. As a reader has pointed out in the comments, it's Leia putting the Death Star plans in R2-D2 as C-3PO watches, like at the beginning of A New Hope.]
Most big fans of the series and Star Wars know that both R2-D2 and C-3PO appear in several occasions in Raiders of the Lost Ark. In the Well of Souls, which is the moment portrayed by this set, they appear in a post on Indy's right as him and Sallah remove the Ark.
Great detail from LEGO and good catch by Lindsay. [Thanks Lindsay]