First off, I'm not sure if this is even possible but considering how long Photoshop has been around and how "powerful" it is, I don't see why I can't. I'm trying to edit sprite sheets with graphics that have lots of transparency on them. I want to move a selection without having the marquee crop itself around image. So for example, if I have a 10x10 pixel image and I select it with a 20x20 pixel marquee, I want to move that selection as the 20*20 box. However, photoshop will automatically crop the selection to 10x10 where pixels/image is present. I need to move the selection as a selection, "empty" pixels and all. How can I do this? Is it even possible?
With an active selection, choose
Select > Transform Selection.
This will allow you to move, or otherwise transform, the selection without it referencing any underling pixels. In other words, it won't auto-clip to any pixels if you move it via the Transform Selection command.
I actually added a keyboard shortcut for the menu item via
Edit > Keyboard Shortcuts because I use it so frequently.
So, you are not going to move only the selection. Your selected area contains some transparent pixels and also some opaque pixels. You want to move at the same time the selection marquee and all pixels - transparent or not - inside it. Especially you want to keep the dimensions of the selection intact, it only moves along the moved pixels.
Have a dummy layer. After making your selection marquee fill the selection in the dummy layer. Select in the layers panel at the same time the actual content layer and the dummy layer. Now you can move the content, filled dummy and the selection at the same time without losing the dimensions of the selection.
I guess you already know that anti-aliasing must be turned off in all tools when making pixel art.