I would like to get the current theme. It could by a code to display current theme in the Status Bar. It could be by going to the current theme picture when Themes is first opened. It could be by listing the current theme name in Themes.
There isn't really a concept of an active theme. There's a "last loaded" theme, but you could have subsequently changed or reset every aspect of it (or left the settings but deleted the theme they came from), at which point you aren't really using that theme anymore, even though it was still the last one you loaded.