If you've got written permission from the rights holder to re-use something for a specific purpose, that's all you need, but make sure you know where it is in case you need to provide evidence of the agreement later on.
Importantly, make it clear you've got permission whenever you re-use the item, for example by stating Presentation used by the permission of the rights holder. The rights holder may even supply you with a preferred form of words, e.g. ©2018. Image reproduced by permission of So-And-So Publishing.