golden serpent
Click on the image once, then you can use CTRL and SHIFT to zoom in and out, and the arrow keys to move around.
If you are on an Apple device, drag your finger on the image to pan around. Pinch/unpinch on the image to zoom in and out.
Wow! I didn't think I could pull it off, but I got even larger than before! This one is 72"x108" at 240ppi (pixels per inch). The PS file is 3.45GB, and I was forced to save it as a Large Document Format (.psb) file.
Can't wait to see how big I can go next! Although, this one took quite a while just to perform certain functions - like saving. The saves typically took about 10 minutes.