Currently DIKSHA portal allow following file types for Images .
jpeg
jpg
png
Please make sure to upload only the supported image types.
You can check the type of file using any online tools. (eg . https://htmlstrip.com/mime-file-type-checker)
Please note:
1. You cannot change the file format by changing/renaming the filename.
2. If you upload an unsupported file, the content publishing will fail