You can put an image instead, and do it like this:
HTML:
<img src="/images/uploadButton.png" id="upfile1" style="cursor:pointer" />
<input type="file" id="file1" name="file1" style="display:none" />
JQuery:
$("#upfile1").click(function () {
$("#file1").trigger('click');
});
CAVEAT: In IE9 and IE10 if you trigger the onclick in a file input via javascript the form gets flagged as 'dangerous' and cannot be submmited with javascript, no sure if it can be submitted traditionaly.