I am also facing the same Issue. I am storing camera photo from Power App to Sql Server table where table column datatype is 'Image'. But when I try to display image/Photo in Power BI it does not show properly and only one small line appear in report (I have added "data:image/png;base64" before the binory part of the Image in Power BI ).
I also have observed base64 increases the size of the string which exceeds the limitation. But I tried by using SQL compression function also but no luck.
I am suspecting that this issue is due to having size more than its max limit in Power BI. If this is so then how to compress or resize the image to be able to visible in Power BI