@romantica
Hi,
look to your style css in your theme to this line, if you dont have it just add it, after - /* Latest ads list */:
/* categories image */
.home #main .categories .category h1 .category.your category name{ background: url(images/your image name.gif) no-repeat; padding: 30px; padding-top: 14px;}
.home #main .categories .category h1 .category.cars { background: url(images/vehicle.gif) no-repeat; padding: 30px; padding-top: 7px;}
.home #main .categories .category h1 .category.realestate { background: url(images/realestate.gif) no-repeat; padding: 30px; padding-top: 13px;}
green - your categories
blue - image name
upload your images to your theme/images folder
rename categories (green) to current name of your categories
set the right name (blue) of images
css
add lines of categories in css as much as you need
regards