Depends on what "a little NAS" means to you, and what interfaces you need. But in general, most any PC made in the last 20 years would work for as simple and small storage server.

Well, something like network mounted 4 TB of space for photos, some movies, stuff like that?!?

Definitely. Bottlenecks will probably be network and storage type. You can probably get a cheap mini PC and add some disks to it.