We do not have any logo rights or other similar clauses in our contracts — Legal doesn’t want them, I think because many orgs redline it out.
I also actually advocate against using case studies and agreement to be a reference for net-new prospect contracts. While obviously we hope for the best, we have no idea if they will be a good story or reference and it’s hard to enforce. I am ok with using it as a price negotiation tactic at renewal as Lauren mentioned, assuming the customer is otherwise happy and seeing great results.
For new sales, I am ok with giving discounts in exchange for logo usage sign off or (with our input/approval) a quote about why they chose us and/or inclusion in a press release.