I quickly tried to drag and drop a file and i got some compile errors. The path was using "\" which i changed with "/" and then it worked and i could compile. But Metasfresh is using a path so it's probably adding it before the path given by jasper.
For example, for Logo we have set the following path "de/metas/generics/logo.png". The file can be found in [...]jasperreports/de/metas/generics/logo.png.
Please make sure your .jpg file is somewhere under [...]jasperreports/de/metas/ and add the path like in the example above "de/metas/....jpg".
I hope it will work. If not, i'll think about other solution.