How to change widget's icons in the service-links module?
CSS solution for position:
for services widgets (FB, pinterest, linkedin) you can not change images, for General Services (twitter, G+) you can upload your own images.

Here is my CSS code and links appear centered inline.

/* services share links */`
.service-links ul li {
 text-decoration: none;
 display: inline;
 overflow: hidden;
 list-style: none;
 padding-right: 10px;
 vertical-align: baseline;
 float: left;
 }

.service-links li {
 display:inline;
 vertical-align: bottom;
 position: relative;
 }
.service-links .service-links-linkedin-share-button {
top: 5px;
}

.service-links .service-links-facebook-share {
bottom: 5px;
}