I FOUND THE FIX on
http://www.zen-cart.com/forum/showth...+size+wishlist

Ill paste it here...

Modify line 76 in /catalogue/includes/templates/YOURTEMPLATE/templates/un_wishlist_find/tpl_un_wishlist_find_default.php
Code:
<?php echo zen_image(DIR_WS_IMAGES . $products->fields['products_image'], $products->fields['products_name'], '', '', 'class="productlist"'); ?>
Replace with: (modify SMALL to desired size):
Code:
<?php echo zen_image(DIR_WS_IMAGES . $products->fields['products_image'], $products->fields['products_name'], SMALL_IMAGE_WIDTH, SMALL_IMAGE_HEIGHT, 'class="productlist"'); ?>
and

Modify line 93 from the original code in
/catalogue/includes/templates/YOURTEMPLATE/templates/un_wishlist/tpl_un_wishlist_default.php from this:
Code:
<?php echo zen_image(DIR_WS_IMAGES . $products->fields['products_image'], $products->fields['products_name'], '', '', 'class="productlist"'); ?>
and replace with:
Code:
<?php echo zen_image(DIR_WS_IMAGES . $products->fields['products_image'], $products->fields['products_name'], SMALL_IMAGE_WIDTH, SMALL_IMAGE_HEIGHT, 'class="productlist"'); ?>