For customers, leads and companies, i would like to be able to create custom user types

I would like to be able to create our own types of users to be included with the default types you already have - for example, we do have a lot of upgrades and would like to be able to search for customers or leads with the "Upgrade" type. This would make the CRM a little easier for us to use if we could add our own types or have you add more types in.