Based on her website (http://www.gahako.com/kikakumono.htm), the characters are from YGWORKING!!, which means that they're technically also Wagnaria staff (see here: http://www.gahako.com/kikaku/k-2.htm).

More proof - the comics that the other unnamed characters appear in are labeled as WORKING!!特別編 or Working!! Special Edition (I think).

According to what I've read, these are two sets of characters working at two different Wagnarias. The ones on the right are from the web koma on Takatsu Karina's homepage "Doubtful" (which is also titled "WORKING!!"), while the ones on the left are the Young Gangan/anime characters.