I never felt pressure to give gifts to volunteers, but I do feel like I always want to share more opportunities with those who are interested.  

I did a research project in school on why volunteers offer their time. It was very specific to the institution, but most of the volunteers said they volunteered because they liked having the opportunity to learn and share their knowledge with others. They definitely appreciated things like free admission to the museum for their immediate family members, being taken on field trips, and a deep discount at the cafe, but a lot of people were there for the experience. They volunteered because they felt like they were contributing to something and also receiving back knowledge and appreciation. You can make volunteers feel truly included with the institution by letting them share their talents when they have ideas outside of the normal roles, or giving volunteers behind the scenes insight with staff and upcoming exhibits. Sending a birthday card or a get well card when someone is sick goes a long way too.

That said, as a volunteer I always appreciate getting a t-shirt when I volunteer for a big special event day. They're dual purpose because public who don't regular visitors knew who to ask question to, since all star and volunteers wore them that day.

Hope this helps, let me know if you want to discuss further!

Samantha Roberts