At present you can only select either Text, Date o currency when adding a field for an asset. Adding a user categories would allow an asset to be assigned to a user and show up under assets. for e.g  User A is allocated a Company Vehicle. allocation inspection occurs and the user is now has that asset in the dashboard. 

E.g 2 User B is allocated tools from a store to go to site and complete a task. The allocation of tools is recorded in Assets and sits with the User until they are returned and a inspection including return of tools is completed.