What uses less memory?
Use 1 object sprite for each image like this:
<img src="https://dl.dropboxusercontent.com/u/72359481/PA%C3%87OCArule2/images/backcave-sheet0.png" border="0" />
Or images in frames of 1 object, and use the frames:
<img src="https://dl.dropboxusercontent.com/u/72359481/PA%C3%87OCArule2/images/chao-sheet0.png" border="0" />