How to display different sets of images per page in sidebar?
Create as many views as content units.
  
  Is there any other cleaner way of doing this?


Yes, you do not need to create a View for each of your nodes/pages/content. You can create a dynamic view which automatically passes the Content ID to Views.  


Create "Four Images" content type set up as a single multiupload image field.
Add these "Four Images" to you node.
Create a View Block


 


In View, for Fields, add your image
Click on Advanced (far right), for Contextual Filter add ID .Provide default value, Content ID from URL. (Note: The view preview will go blank, which is normal, since the View edit page does not have a Content ID.)





Go to blocks (/admin/structure/block), and add the View block to a region. For Visibility settings select the content type that you want this to appear in.