As part of improving the look and feel of the desktop, I propose that some elements which are stationary as of now, be animated to indicate what happened behind them. See the examples below. The first few are very similar to how the new notification bell icon is animated on new notification.
Password field wiggle on incorrect password like GNOME plans to do it, it could be faster and subtler, with a red label appearing below the fiend saying "Authentication Failed" or "Incorrect Password". The password dialog should not resize, and as soon as the user touches the field and changes a character or starts typing in it or clicks on the eye symbol, the warning should disappear.
Trash highlighting on item deletion in Dolphin: When a file or folder is moved to trash in Dolphin or file dialogs, the trash entry in the Places sidebar should draw attention for a second in some way. There are multiple ways to emphasize it.
a) (hard to implement and resource-hogging) The trashed item could start flying towards the trash, while shrinking and fading out at the same time.
b) The trash icon could be animated to open the lid for a short time, catch a piece of crumbled paper flying into it, then close the lid back.
c) The trash icon could wiggle subtly for a second.
d) The trash icon could smoothly become larger by 20-40% and then shrink back.
e) The trash icon could turn red for a second.
f) The trash enry text could become bold and/or red/blue for a second, with a smooth transition into and out of the emphasized state.
g) The trash entry could become highlighted with a light gray background for a second, with a smooth transition into and out of the highlighted state.
Informative animations in System Settings to communicate what certain functions do
Here I am thinking about a small animated frame in Night Color page for example, which would show a symbolic KDE desktop with a symbolic Sun. Shortly after the Sun turns into a Moon (indicating sunset), the desktop is tinted yellow indicating what Night Color does. In manual mode, the Sun/Moon could disappear. In "Custom time", it could show a clock. The yellow tint could respect the warmth setting.
Another example might be one-clik vs double-click selection. The symbolic frame could have some folders in it and a cursor. In one-click mode it clicks on the '+' selection button and the folder becomes selected. It clicks on the folder and the view turns into files. In double click mode, there could be one click which would select it, and then a double click would go into it. Each click could be represented by a bluish ripple spreading from the tip of the cursor.
Here are my suggestions for now. I will update this when I have more ideas of subtle animations like these. I think that small animations like these could help the desktop feel more responsive and snappy, while making it easier to use as these help the user intuitively recognize what is happening in their computer and what did they do.