Say you have 10 different versions of the same image, like your feedburner count. Here is some sweet htaccess rewriterules and caching directives you can use to show a different version based on the time.
RewriteEngine On
RewriteBase /
RewriteCond %{TIME_SEC} ^.([0-9]) [NC]
RewriteRule ^feed\.gif$ /feed%1.gif [NC,L]
RewriteEngine On
RewriteBase /
RewriteRule !\.gif - [S=4]
RewriteCond %{TIME_SEC} ^(0|4|8|12|16|22|26|30|34|38|42|46|50|54|58)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^feed\.gif$ /zi/feed1.gif [S=3]
RewriteCond %{TIME_SEC} ^(1|5|9|13|17|23|27|31|35|39|43|47|51|55|59)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^feed\.gif$ /zi/feed2.gif [S=2]
RewriteCond %{TIME_SEC} ^(2|6|10|14|18|24|28|32|36|40|44|48|52|56|60)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^feed\.gif$ /zi/feed3.gif [S=1]
RewriteCond %{TIME_SEC} ^(3|7|11|15|19|25|29|33|37|41|45|49|53|57)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^feed\.gif$ /zi/feed4.gif
In order for the image to be reloaded on each page-view of the site, I set up some anti-caching headers in my .htaccess file. First I unset the far-future Expires headers that I normally send with images, and then I instruct browsers to check the image every request to see if it has been modified.
Header unset Expires Header unset Last-Modified FileETag None Header set Cache-Control "no-cache, must-revalidate"
Awesome! You can read the full article here: 
Rewriting Feedburner Counter, Cache, and more with htaccess rewrite..
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