Round corners for user2 module

I have a picture with all sponsor logos under user2 and it has rounded corners but this is just one picture.
joomla.bcmarburg.de

I would like toadd round corners to the user2 module in case a background picture is added so that the background picture always has round corners.
I added the following code to the user2 moduletable in template.css.css

.user2 .moduletable {
margin:5px;
padding-bottom:3px !important;
padding-top:3px !important;
background-color:#343594;
-moz-border-radius:10px 10px 10px 10px; /* Firefox */
-webkit-border-radius:10px 10px 10px 10px; /* Chrome, Safari */
-khtml-border-radius:10px 10px 10px 10px; /* Konqueror */
border-radius:10px 10px 10px 10px; /* CSS3 */
}

I figured out that this would only have an impact if I am assigning a background color. But not every module assigned to user2 shall have a background some of some shall apear transparent as it is with the picures now below the sponsor logos

Is there a chance to create another module like user10 and allocate it in the layout below user2 one with background and user2 without?
What would be the code?

Can you please tell us more directly what you need?

On the page joomla.bcmarburg.de the template position "user2" has a transparent background. I would like to add the opportunity to add in the user2 area modules which have a background with round corners. Since round corners could only be visibly applied if a background color is assigned, I currently could have elements in user2 with or without a background. Thus is there a way to add another position below user2 in the template called e.g. "user10" for which I can set a colored background. Similar to the top left/top right column and left/right column?

I probably found a solution since I could assign a module to advert1 section. If nothing is displayed for 2-4 it appears as a block across the page but I wasn't able to define the necessary cody in template.css.css for the blue background with rounded corners.
I changed in template settings the background color of the bottom modules to blue but how can I define rounded corners?
Is there also a chance to distinguish between the background color of modules appearing in the advert 1-4 position and the user5-8 position?

I tried adding this to template.css.css but wasn't successful:

.advert1 .moduletable {
margin:5px;
padding-bottom:3px !important;
padding-top:3px !important;
background-color:#343594;
-moz-border-radius:10px 10px 10px 10px; /* Firefox */
-webkit-border-radius:10px 10px 10px 10px; /* Chrome, Safari */
-khtml-border-radius:10px 10px 10px 10px; /* Konqueror */
border-radius:10px 10px 10px 10px; /* CSS3 */
}

Best use suffix for each module but with first blank char like " rounded1" then adding this css class would do:

.rounded1{
...
}

this would be universal not matter where module is located

Ok what would be the code?
Shall I Insert a general section like this:?

.round1 {
-moz-border-radius:10px 10px 10px 10px; /* Firefox */
-webkit-border-radius:10px 10px 10px 10px; /* Chrome, Safari */
-khtml-border-radius:10px 10px 10px 10px; /* Konqueror */
border-radius:10px 10px 10px 10px; /* CSS3 */
}

In IE9 the corners are not rounded, is there another syntax error?
I used border....