Use Bootstrap FileStyle, which is used to style the file fields of forms. It is a plugin for a jQuery-based component library called Twitter Bootstrap
Sample usage:
Include:
<script type="text/javascript" src="https://stackoverflow.com/questions/1944267/js/bootstrap-filestyle.min.js"> </script>
Via JavaScript:
$(":file").filestyle();
Via data attributes:
<input type="file" class="filestyle" data-classButton="btn btn-primary" data-input="false" data-classIcon="icon-plus" data-buttonText="Your label here.">