Models for different property editors and corresponding values converters are (scattered) in multiple namespaces.

[soreng]

The new media pickers handles a value of type MediaWithCrops found in Umbraco.Core.Models. On MediaWithCrops there is a property LocalCrops of type ImageCropperValue. This is found in Umbraco.Cms.Core.PropertyEditors.ValueConverters. The Crops property is of type ImageCropperCrop, that is a class insiede the ImageCropperValue. All the models seem to be in the Umbraco.Infrastructure assembly.

Link that is used by the Multi Url Picker, lives in Umbraco.Cms.Core.Models, found in the assembly Umbraco.Core.

It seems like a bit of an oversight, and you end up with a lof of usings scattered in views / configuration. This may be caused by the Multi Url Picker being a bit old, but as a guide for a PR, it would be nice to know the preffered naming.