<$list filter="[tag[png]] [tag[jpg]] [tag[gif]]">
[img width="128px"[<<currentTiddler>>]]
</$list><$image> widget. So something like:
<$list filter="[tag[png]] [tag[jpg]] [tag[gif]]">
<$image width="128px" source=<<currentTiddler>>/>
</$list>
Good luck!
-- Mark