If you want to change the loading image,
please change the css code as in line 206-217 of \wp-content\themes\aside\style.css(or put the css code to custom css box in themeoption) and replace the \wp-content\themes\aside\img\loading.gif as your gif:
.site-loading .ux-loading-transform,
.page-loading .ux-loading-transform {
display:none;
}
.page-loading .ux-loading,
.site-loading .ux-loading {
background-image: url('img/loading.gif'); margin-top: -56px;
}
.page-loading .ux-loading,
.site-loading .ux-loading {
display: block;
}