3
actually you can try do this....
step 1create the block in block admin with a unique name title example "gallery".
step 2edit yours themes "theme_blockcenter_r.html" and amend it to this code(themes example is x2t):
<{if $block.title =="gallery"}>
<{$block.title}> ///this is to call to block gallery
<{$block.content}> ///amend as you wish
<{else}>
/// this is for normal block
/// amend as you wish
<div class="blockTitle"><{$block.title}></div>
<div class="blockContent"><{$block.content}></div>
<{/if}>
step 3 upload "theme_blockcenter_r.html"
i have use this in my site and it work perfectly and i can change any block themes without many modification.