When the DLL is first loaded it will most likely show up as with 'Image' in Process Explorer's Mapping column, so that the code from your DLL can be executed.
If at some later point a resource from your DLL is required then it may show up a second time in the list but this time with 'Data' in the Mapping column, e.g. if the LOAD_LIBRARY_AS_DATAFILE
flag is used to LoadLibraryEx