General:
* A group of models (simple and straightforward)
* A bevy of models (implies a large, attractive group)
* A panel of models (suggests a group for discussion or evaluation)
Specific:
* A troupe of fashion models (for runway or promotional models)
* A team of scale models (for architectural or engineering models)
* A collection of model airplanes (for hobbyists)
Ultimately, the best collective noun depends on the specific type of models you are referring to and the tone you want to convey.