There are several synonyms for the term "standing around." One can use the phrase "hanging out" or "loitering" when describing individuals standing around with no defined purpose. "Lingering" and "loafing" also convey a similar sense of passively waiting or lurking without direction. "Idle" or "idly milling about" works great to depict the aimless movement of individuals in a particular place. If the individuals are standing around waiting for something to happen, "anticipating" or "expecting" may be the best terms to use. In conclusion, while the term "standing around" is aptly descriptive, one can find alternatives to diversify their language and add variety to their vocabulary.