If you want to customize the block.tpl.php for different blocks. The Block Theme module could serve this purpose well.
3. Then we need to create the block--blocktheme--eureka.tpl.php. I am using the Omega theme so i copy the block.tpl.php from the Omega core to my Omega starter theme folder and rename it to block--blocktheme--eureka.tpl.php.
5. Go the your block configuration page where you could select the Block Theme.
Reference: Drupal Module – Block Theme