How do you Change html controls and edit classes in appinventor open source?

Hello Everyone im new in app inventor open source development,i change some css in menu but i want to edit in html tags like (paragraph text , classes) how to do that :smile: ?
also i want to change icons for these controls (Button,Label,Checkbox,Listview) because i change the images but not changed i think the icons saved in database as stream..:

and thanks :smile:

You can change from appengine/client/images