An essential part of a successful fundraising campaign is making it as easy as possible to donate. Once a user gets to the donation page, familiar imagery and styling reinforces the brand, and a clear UI streamlines the giving process.
I've been involved with either designing or redesigning several donation pages from the ground up, which of course entails a more involved process than just creating a header image and flowing in text. A lot of the UI/UX design choices are informed by preexisting creative for that client as well as general best practices, such as aiming to keep part of the form in view upon landing to motivate the user to start filling it out.