hi Oliver.
It's a simple issue of templates.
Edit your myablum*_categories.html like this:
line 18
<{foreach from=$cat.subcategories item=subcat}>
<{if $subcat.number_of_subcat}>
<a href="<{$mod_url}>/viewcat.php?cid=<{$subcat.cid}>"><img src="<{$mod_url}>/images/folder16.gif" width="16" height="16" alt="" /><{$subcat.title}><img src='<{$mod_url}>/images/subcat.gif' width='15' height='15' /></a> <br />
<{else}>
<a href="<{$mod_url}>/viewcat.php?cid=<{$subcat.cid}>"><img src="<{$mod_url}>/images/folder16.gif" width="16" height="16" alt="" /><{$subcat.title}></a> (<{$subcat.photo_small_sum}>) <br />
<{/if}>
<{/foreach}>
I'll consider that the default template should use <br /> or not.