PostageStamp

You can add this node to your script to display a thumbnail render of the output at the current frame or a frame of your choice. This node does not alter the input image in anyway.

By default, the postage stamp is always updated to match the current frame. To change this behavior, press Shift+S to open the Preferences dialog, go to the Node Graph tab, and set postage stamp mode to Static frame. Then, set static frame in the PostageStamp node properties to the frame you want to display.

Note:  If the frame number you use is outside the frame range for the node, it is clamped to the first or last frame in the range.