Libre office has Draw software in the office suite. You can make use of that to draw some art. It comes with some specific set of tools. It can be also used to make the template based art. If you are not unsure you can also use the online tools such as canva and picmonkey. You'd be able to use those tools, and export the result in jpeg or PNG. And that can be later imported into the Libre office doc. It has worked like that for me and you can too use this method.