Yea, maybe not a shirt, but hell, send them some nice coffee or some snacks or something. My current job is probably at least 50% implementing stuff my company bought, and for one of them, they had an on-site meeting about the implementation/proof of value stuff and they offered to buy everyone coffee/tea/whatever at a coffee shop by our office before the meeting and that definitely helped me be a bit less grumpy about the work.

Any sort of "congrats on launching/implementing our stuff" gift is at least an acknowledgment of the work put in to help the sales team land their contract, and that helps keep the relationship on a good footing.