Should there be an alias between braids and braided_hair? They seem like they refer to the same thing.
Plaits and braids also seem to be the same thing, or sufficiently similar that I'm not sure if anyone would really appreciate the difference.
About plaits as they relate to braids
Google's dictionary definitions (plaits, braids) suggest that the two are the same or very, very similar.
Wikipedia's page on plaits is a disambiguation page between braids, a disused term for pleats in clothing, and an anatomical feature of some gastropods.
There are currently only 4 posts using the tag, all of which refer to braided hair.
Granted, with only 4 cases of plaits we could just change those tags and call it a day, since it appears that those are the only 4 images that have been tagged that way, and the most recent tagging was May 2011. An alias would just make sure people can't resurrect the tag in the future.