Here is a simple way to do it usingMulticolumn, which is new in V10. I use a 4 x 4 grid with a list of three pictures

Multicolumn[
  Item[PopupWindow[#, #, WindowSize -> {All, All}], ItemSize -> 10] & /@ 
    pictlist, 2, Frame -> All]

And clicking on one the thumbnails produces

Here is a simple way to do it usingMulticolumn, which is new in V10. I use a 4 x 4 grid with a list of three pictures

Multicolumn[
  Item[PopupWindow[#, #, WindowSize -> {All, All}], ItemSize -> 10] & /@ pictlist, 
  2, 
  Frame -> All]

And clicking on one the thumbnails produces