[[!migxLoopCollection? &packageName=`gallery` &classname=`Gallery` &sortConfig=`[{"sortby":"title","sortdir":"ASC"}]` &where=`{"image_names:LIKE":"%John%","published":"1"}` &tpl=`mGalleryAlbum` ]]
&where=`{"image_names:LIKE":"%John% or %Tom%","published":"1"}`
This question has been answered by just_nico. See the first response.
&where=`[ {"image_names:LIKE":"%John%"}, {"OR:image_names:LIKE":"%Tom%"}, {"published":"1"} ]`