From what I can remember from early draughts of ESB Vader's little home from home was volcanic and populated by demonic looking gargoyle creatures so if Geonosis were to resemble that it would have look almost exactly like Mustafar and the Geonosians would be dark gray or black with glowing coals for eyes.

If you are going for that look why not merge the two locations together?

Possibly impossible but what if instead of some anonymous hanger building, Shaak Ti has established a Republic command centre and when Obi-Wan and Anakin face off Dooku they are trying to save her...leading to the re-established deleted scene in ROTS.

This would create something a bit more like the dynamic of the end of ESB (though Shaak Ti is not a character we have enough investment in but it's difficult to stick in a major character with the available material at least she is in full make up).