Credit for this mod goes out to both AYA and Yuniargo.
I started with the ItemDisplay.xml from AYA's UI. I then took the part of the code from Yuniargo's that added a guild logo image. I then made a simple logo for my guild and changed the file name in the ItemDisplay.xml file.
I also made the icon smaller.
I hope you like it. And you can easily change the image just like I did.