My advice is to wrap each of your <img> tags with anchor tags and enter the fullsize image as a link like this:
<img src=”” id=”image” />
<li><a href=”teambuilding_album/fullsize/capoeira_workshop_.jpg” onclick=”return selectImage()” ><img src="teambuilding_album/thumbnails/capoeira_workshop_.jpg" alt="Malmö Capoeira" width="100" height="100"></a></li>
I also think it will be more clear to use <ul> and <li> tags as above.
Note: I have not tested the above code, but the idea is there.