There is not a very flexible filtering function, but the panel at the bottom allows you to show only requests for a specific document or connection type:

You cannot just exclude images, but this should help.
You can also press Control / Command + F to search for a specific line in the query list and check the "filter" box to hide queries that do not match:

Toronto Raptors Jan 31 '13 at 23:49 2013-01-31 23:49
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