Hi Pete, spacer.gif is the placeholder image for the lazy loader.
In skin/reboot/product_thumbnail.tpl you can replace...
Code:
{if !$notlazy} src="{$AltImagesDir}/spacer.gif"{if $image_x ne 0} width="{$image_x}"{/if}{if $image_y ne 0} height="{$image_y}"{/if} data-src="{else}src="{/if}
With...
Code:
{if !$notlazy} src="{$AltImagesDir}/spacer.gif" data-src="{else}src="{/if}
The {if !$notlazy} code is correct as it is.