After struggling with the issue, I finally found the solution to my initial problem:
@media (max-width: 480px) {
.site-title a {
background: transparent url("http://examplewebsite.com/mobilelogo.png") no-repeat scroll 0 0 !important;
overflow: auto;
}
}
}
@media (min-width: 480px) and (max-width: 768px) {
.site-title a {
background: transparent url("http://examplewebsite.com/tabletlogo.png") no-repeat scroll 0 0 !important;
display: block;
}
}
Furthermore, I managed to address the gap between the logo and the main content by implementing the following code:
.header-full-width.header-image .site-title a {
background-position: center bottom !important;
}