Those examples aren't working for a few reasons.
When specifying an image URL in CSS you need to use the whole thing starting with http, not just the file name. Also one of the tricks relies on you creating one image file out of the two different pictures and then flipping position between them. It doesn't look like you've done this so it won't have any effect. I would also recommend uploading your images in the size that you're going to display them, otherwise it is a waste of people's bandwidth and will make your site load slowly. Most of your photos are big enough to be desktop backgrounds but you're only displaying them as tiny thumbnails.
Here's the method I would recommend. In your post or page switch to the HTML editor and add the following code. Note that the ID will need to be different for every set of rollover images you want to include.
<a id="roll_one" href="LINK-URL">Description text that will not be displayed</a>
Then you need to add the following to your CSS. Remember if you're adding multiple rollovers to change the identifier following the hash. You'll also need to explicitly set the width and height of the original image in the code here.
#roll_one {display:block; width:300px; height:200px; text-indent:-999em; background:url("IMG1-URL");}
#roll_one:hover {background:url("IMG2-URL");}
That works fine on my test blog using images that are exactly 300 by 200 pixels. Try it out and if it doesn't work then let me know.