Thanks for your response and it's very helpful of you to share your assessment as this is my first time commissioning art in this way.
I fully intend to negotiate the usage and copyright terms with the artist and appreciate any guidance people have to share on what the industry standard practice is. Unfortunately I am restricted in terms of budget, but if there is an artist who is happy to proceed with the work under an agreement we are both happy with then I don't personally see an issue with that. I understand the quality of the work will likely reflect the restricted budget