You probably cannot convert pictures (like JPEG format) to a OpenDocument template (.otg). But much like in any other document, you can import pictures to it, which means you can also prepare templates with some pictures. Hence "conversion" of this kind is doable, but it is not a file conversion in true sense.
Convert JPEG bitmap image format to OpenOffice.org graphics document template.
We have found 2 software records in our database eligible for .jpg to .otg file format conversion.
Multiplatform software - convert jpg to otg on any platform
Graphic editor for diagrams and simple graphics from OpenOffice.org suite
Convert from jpg file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned jpg to otg. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Graphic and diagram software from LibreOffice suite