i want to upgrade minibb without having tpl files, having just php and html, css and js but not tpl

well minibb is using smarty
but i remove smarty...

tell me the way to remove smarty and customize minibb...since i dun know nothing about
smarty

Sorry, but your question is not clear.

miniBB is not using Smarty, it's using it's own templates parsing engine. Regarding upgrading miniBB refer to this thread: Upgrade and Upgrading / Migrating guides as well as Upgrades history from our Downloads.

How can we use Border-image in CSS ?

Black border for all images:

img { border: 1px solid #000; }

This can be targeted to only images inside post messages by this (if you use default template):

div.postedText img { border: 1px solid #000; }

how can I put in border image?

like bakcground image?

.tbCel1{
background-color:#9AD991;
background-image: url(img/cel01.gif);
}

but also use it in border line images?
I didn't get what you mean?

I guess background image over an image is a no-no..