The tympanum mosaic in the doorway niche features the Lamb of God presiding over the Rivers of Paradise, from which drink four deer (in allusion to Psalm 42:1). Below this is a mosaic, damaged by the later and rather brutally created doorway, featuring, from left to right, Theodora, the mother of Paschal, St Praxedis, the Blessed Virgin Mary and St Pudentiana. Theodora is depicted with a square halo, indicating that the image was made when she was alive.

(Another photo of the mosaic here)