Hello and welcome,
I agree that the main and supporting photos need to be improved upon. If this is a mural, it seems like it’s larger than just 1 character (Sailor Moon appears to the right, so why not include the full mural). You should try to show the entire mural instead of one part, if possible.
And the supporting photo should show the POi with the surrounding area, not just the surrounding area. I have no idea that this is in the student union from any of your photos, as none of the photos show the mural with the surrounding area. It’s important to show the POI within the surrounding area, especially for indoor POIs, so we can do our best to place it as being where you say it is.
I would recommend considering taking several supporting photos showing the POI in the area, and then using the new web submission to resubmit this. Web submissions allow up to 5 supporting photos instead of the 1 that only PoGo allows, so it may be helpful in this situation. More info about web submissions can be found here: