Notes:
rename your image url to coincide with image uploaded:
thus
Code:
<!--buy me a beer -->
<if condition="$post['field22']"><div class="info">
<a href="https://www.paypal.com/cgi-bin/webscr?cmd=_xclick&business=$post[field22]&item_name=Buy me a Beer&amount=3%2e00&no_shipping=0&no_note=1&tax=0¤cy_code=GBP&lc=GB&bn=PP%2dDonationsBF&charset=UTF%2d8" target="_blank" rel="nofollow" title="Click to buy me a Beer">
<center><img alt="Buy me a Beer?" border="0" src="http://www.yoursite.com/images/misc/beer.png" border="0"/></center>
</div></if>
<!--end buy me a beer -->
beer.png to match the uploaded file, included file needs to be renamed accordingly.
Changed my postbit as above to fit in with our style.
Good work Mate