how to delete width and height attributes from image field for particular nodes
You may be able to accomplish this with view modes.  

Make some new image styles for these particular images.  Implement a theme_image_style(), which checks for this new style name and unsets width and height as needed.

If you install/enable Entity View Modes you can create new view modes for your nodes.  Clone what you have for node/teaser to your additional layouts.  For the images, change the display settings to use your new styles.

Next is the part I am not sure what the best solution is.  One way to use the view mode is to use a Panel page for each individual node.  When you add the content, you can set the view mode to one of your new ones.   Otherwise, I would try @PierreBuyle's solution at Using a different view mode with a node.  This essentially overrides the menu page for node/nid to add some additional intermediate logic to set the view mode.