The Sarlacc Pit is a general posting forum and anything not specifically prohibited in the CoC may be posted there. There is no reason why you could not share your cretive efforts regarding your custom mando in the Sarlacc Pit.
InfraFett said:question:
for us who have/or are working on custom mandos, are we allowed to post backstories about our characters? I like the be creative since I'm making a custom. If so, I'm sure We'd have to post it in the sarlacc pit since It has nothing to do with armor building.