Welcome to the Make community!
Try using the replace function to replace %%bgImageUrl%% into {{bgImageUrl}}
e.g.:
Example output string
Hope this helps! Let me know if there are any further questions or issues.
— @samliew
P.S.: Did you know, the concepts of about 70% of questions asked on this forum are already covered in the Make Academy. Investing some effort into it will save you lots of time and frustration using Make later!