How to display an image above the needed window in needed position?
Depending on your needs, and based on how I gotten your question, you probably need something alike Clickclick: 


  “Cliclick” is short for “Command-Line Interface Click”. It is a a tiny shell/Terminal application that will emulate mouse clicks or series of mouse clicks (including doubleclicks and control-clicks) at arbitrary screen coordinates. Moreover, it lets you move the mouse, get the current mouse coordinates, press modifier keys etc.


it's what people advice to be the good compromise for xdotool.

As for conky, probably the closest alternatives for Mac would be:


GeekTool 
GKrellM - a single process stack of system monitors which supports applying themes to match its appearance to your window manager, Gtk, or any other theme.
XRG
Übersicht - "Übersicht lets you run system commands and display their output on your desktop in little containers, called widgets. Widgets are written using HTML5, which means they


are easy to write and customize
can show data in tables, charts, graphs ... you name it
can react to different screen sizes"



But there are no direct alternatives, which fully accomplish the functionality of highly-customizable conky and powerful xdotool. You need to invent something else.