Add html in field

Is there ant way to include the “HTML before/after field:” to be sent with the form?
I have found a way to change the file upload button to a custom button as seen here but my problem is I can’t get the new upload to send the image selected to email as it is styled in the “HTML before/after field:” before the form field.

Also I have tried to style the form input with an id or a class but it doesn’t work should it be .myclass or class=”myclass” in the input CSS

Any help much appreciated

https://ww.wp.xz.cn/plugins/si-contact-form/