LOZ or Custom LOZ most likely as the way it's currently set up is as follows:

All the major tilesets have a separate category as well as a custom title added to it. Ex. Pure, Custom Pure. Newfirst, Custom Newfirst. As well as Just Custom or mixed. That allows people to search the QDB by tileset in addition to Date, ZC version, etc. Just use your best judgment or add a brief description of what kind of graphics you used. You can't really horribly and blatantly err while including this...well never say never I guess...But it'd be pretty hard anyway.