You can print images in TreePad articles in the following ways:
Export the image to a separate image file, then open that file with an image viewer or image editing program that allows you to print it. See Exporting images.
Print the whole article containing the image or, if you want just the image printed, copy it to a blank article and then print it. See Printing an article.
Move or copy the node containing the image to somewhere in the tree where it has no child nodes, then export it as a subtree to a browser or RTF program, which can then print it. See Printing a subtree.