I have done this sort of thing on our asset system because I wanted to create collections of Helpdesk tickets.  You can actually create collections out of anything that has a guid.  I believe that the collection builder in the console only gives you access to computers, but if you select the option to enter SQL directly you can do something like this for example to get a collection of Network Printers

   select [_ResourceGuid] as Guid from vAsset where [Asset Type] = 'Network Printer'

What Altiris is looking for when building a collection is a guid and nothing else, so when you enter your SQL, you can use whatever filters in your where clause you want, but just make sure that the only column you include in the select statement is guid.

I hope this helps!