Instructions on how to create, composite pictures:
1)Scale all images to 600x450px.
2)Add 10px of white space for each end. 
(In GIMP choose canvas size, unclick proportions link, set to 620x470px. Center image.)
3)Open GIMP and create 1800x1350 canvass
4)Drag, rotate and create your composite picture.
5)Scale down to 600x450px.