I cannot give the orginal Kentico code for the GetImage method, but what do you need to do?
If you only want to add an css class to an image you can also do this in your transformation with standard Kentico:
<img class="CLassName" src="<%# GetFileUrl("NameColumnOfYourImage") %>" />
Another example with an news teaser image:
<%# IfEmpty(Eval("NewsTeaser"), "", "<img class="CLassName" alt=\"" + Eval("NewsTitle") + "\" src=\"" + GetFileUrl("NewsTeaser") + "?maxsidesize=100\" />
Good luck and if you want to do something else or more please let us known, probably we can help you further.
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