... new blocks ... ? ... newest images of all main-categories ... ?
... one solution ...
... make a copy from section "Show New Images" in index.php for each main-category and use in sql-query for each ... "WHERE cat_id = XX ... "
... where XX is the cat_id of your main-categories ...
... in each section use instead for all "new_images" -> "new_images_cat_id_XX" ...
... and now you can use in your home.html for each block ... {new_images_cat_id_XX} ...
... and template-design is your part ...
... a hint ...
... make first a test with only one main-category ...
... and if it works ... then make a copy for each other main-category ...