..Its some kinda hard to solve the url problem without knowing the the additional code and settings.

try this:
open index.php
and find

<div id="contenido">
    <div id="tools"><div id="fullsize"<? if ($ancho<=900) { echo ' style="display: none; "'; }?>><a href="<?=PATH_SCRIPT.DIR_IM.$folhost.$name?>" title="<?=$ancho?>x<?=$alto?>"><?=FULL_SIZE;?></a></div><div id="sharethis"><a id="sharing"><?=SHARE;?></a><a id="sharing-close" style="display: none;"><?=SHARE;?></a></div></div>
    <div id="imagen"><a href="<?=PATH_SCRIPT.DIR_IM.$folhost.$name?>"><img src="<?=PATH_SCRIPT.DIR_IM.$folhost.$name?>" alt="" <? if ($ancho>=900) { echo 'width="900" '; } ?>/></a></div>
    

Without knowing the additional script content u can try to change the URL variables to the preview image after uploading. This may cause some errrors.

Solving ur problem my become easyer by knowing the full plugin.

Have you thought about releasing your date-folder plugin? Its some kinda hard to solve the url problem without knowing the the additional code and settings.

Removing chevereto credit suxxx

im having this problem and i don't why

when someone uploads an image , the preview image is shown in an incorrect url , and same problem in viewer

for example
i tried to upload http://chevereto.com/foro/img/smilies/smile.png
the preview image url should be http://fuzzypic.com/images/09212009/smile.png
but it shows like this http://fuzzypic.com/smile.png , and its not working , i mean thats not the real image url
and same problem with viewer http://fuzzypic.com/?v=smilemxm.png

anyone ?