[reefland]

You might do something like this:

{section name=image loop=$images}
{if $images[image].avail eq "Y"}
{if $images[image].tmbn_url}
{section name=image loop=$images}
{if $images[image].image_x > 460}
<IMG src="{$images[image].tmbn_url}" alt="{$images[image].alt|escape}" width="460" />
{else}
<IMG src="{$images[image].tmbn_url}" alt="{$images[image].alt|escape}" />
{/if}
{/section}

This will keep any detailed image at or under 460px in width in or to keep it from breaking a style.