Left/Right columns with background and margin

I'd like to add behind every item (module etc.) which I locate either to left or right columns (e.g. left-top or left) a background image which automaticall adapts its size to the length of the article or module etc.. There should be also a margin between the individual modules (on top or on the bottome.
What would be the code for example for .column_left?
Thx

You can use background image but note that background size property is css3 and not supported by old browsers.

So you add

.column_left{
background-color: transparent;
background-image:url(...path to image...);
background-repeat:no-repeat;
background-size:cover;
}

you would add that to bottom of template_css.css

Thx, but I can't see a margin letting the background shining through between both modules on the left (MBLZ... & DBBL News)
What do I need to add here in order to "differentiate in two two separate blocks, currently it just merges block below block.
joomla.bcmarburg.de

then use module class suffix with first blank char like " mymodule1"

then css would be:

.mymodule1{
background-color: transparent;
background-image:url(...path to image...);
background-repeat:no-repeat;
background-size:cover;
}

Thx but the background is still across the articles according to its size. I need a margin between the module blocks. So I added margin-bottom:5px; as last line in .mymodule1 in template_css.css but nothing changed?

can you illustrate somehow what you want also link to page would be good