404 error using image pool iRule

I'd guess the issue is that a request that should go to the default pool on the VIP is going to the image pool. You could explicitly add a default case to the iRule or add a OneConnect profile to the virtual server to prevent this.

  
 when CLIENT_ACCEPTED {  
     Save default pool name  
    set default_pool [LB::server pool]  
 }  
 when HTTP_REQUEST {  
    if { [HTTP::path] ends_with ".jpg" }{  
       pool images.xyz.com  
    } else { 
       pool $default_pool 
    } 
 }  
 

For details on OneConnect and pool selection you can review Deb's articles linked from this post:

http://devcentral.f5.com/Default.aspx?tabid=53&view=topic&postid=30865&ptarget=30875

and here:

http://devcentral.f5.com/Default.aspx?tabid=53&forumid=5&tpage=1&view=topic&postid=3392157229

Aaron