Support Forum

The shadow is coming from a CSS setting in your WordPress theme. It is setting a shadow for the whole site.

What you would need to do is add some CSS somewhere to overwrite it for the forum or remove it from your WordPresss theme if you don't want it on other pages.

Something like

#spMainContainer {
 text-shadow: none;
 }

Will remove it from your forums only. You would need to add to either the WP theme CSS or CSS override if your theme has that ability. You could add to your Simple:Press theme but you don't have a custom one so it would be overwritten on any SP theme updates.

On the button if you are talking about the icon next to the Group name that is done by uploading a new on in Forum Admin > Manage Forums > Custom Icons. Then Manage groups and forums > edit group and select that icon.