Are you using the importrange and then adding additional columns in the google sheet? If so, just like using a UNIQUE formula, you run the risk of data becoming misaligned because the data in the importrange is not directly linked to the row that contains the additional column data. I avoid doing things like this at all costs because it’s too easy to have corrupted data if things change and become misaligned. Instead I have used scripts in the past to only add new names to a sheet if the name doesn’t already exist. This was instead of using a UNIQUE formula to bring names into several other sheets. Using the script instead preserves the name in the row it was written to initially. I have since restructured my app and data so I don’t need to do that anymore, but it’s a safer way if you need it. If you are having the members sign in to change their info, the using user profiles would create a row for them automatically in a separate user profile sheet.
What I would do is have a separate sheet (new user profile sheet) that contains editable member data, such as the member photo. Allow that separate sheet to be edited by the user instead of the sheet that contains the imported member data. From here you can either display the imported members sheet and use a relation/lookup to pull in the updated photo from the user profile sheet, the use an If/Then column to determine which photo to display. Or you can display the user profile sheet and use a relation/lookup to pull in all the info from the imported sheet. Pick whichever method is easier to maintain.