Ishimoto - Center First & Last Image

I have everything setup the way I want it on my entire site except I can't figure out how to center the first and last image on my welcome page. The only custom code I have on the site is below which was just to add padding to the gallery on that page. Any thoughts on how I can make sure that the first and last image (all images, for that matter) is centered on the screen? My website is www.jordanpowers.com .

@media only screen and (min-width: 801px)
    { 
.slide img {
             border-left: 10px solid;
             border-right: 10px solid;
             border-color: white !important;
}
}

@media only screen and (max-width: 639px)
    { 
.slide img {
             border-bottom: 2px solid;
             border-color: white !important;
}
}