Sadly, we can not currently auction bags. I believe this is because there is no way to keep track of what is inside the bags. If we could auction bags, one could then start auctioning cubimals and such by simply putting them in the bag. This could easily cause scams to break out. If we could see what was in the bag before we buy it, that would make things much safer and easier.
I don't think having something extra in the bag would be a bad thing for the buyer. But I was thinking of selling empty bags. Not a package of things, although that could be nice, selling set of things.