Yes! I have the same question.
I just overwrite it with an background image.
But the background image is not centered. Because the DIV has width:100% and the text-icon is text-align: center;
this is my idea, but the icon is on the left side, not centered.
figure .fa-file-text-o {
background: rgba(0, 0, 0, 0) url("images/new-icon.png") no-repeat scroll center center;
height: 36px;
text-indent: -999em !important;
width: 36px;
}