Solution : https://service.sap.com/sap/support/notes/484878 (SAP Service marketplace login required)
Key words : 
sap-public-bw-customer-images, mime/customer/images/mypicture, /mimes/webrfc/bw/images, /mimes/webrfc/bw/mypicture, terms business information warehouse, precalculating bw web templates, mime/customer/images/, /mimes/webrfc/bw/, mime/customer/image/, bw-specific parts
Related Notes : 
       
| 765536 | Query view after upgrade not visible in the Workbook | 
| 628140 | Handling charts in the Web Application Designer; Libraries. | 
| 597258 | Conversion terminates (PARSE_TEMPLATE)/Web template empty | 
| 597050 | Precalculating Web templates: no conversion during upgrade | 
| 513795 | Error/termination during 2nd conversion step of Web objects | 
| 484519 | BW 20B/21C Web template check program | 
| 484390 | Storing own MIMEs (e.g. stylesheets) in the MIME repository |