Not yet! But soon you will be able to add your own sentences. We're creating a web app to allow you to do just that and to record those sentences easily with the help of a tutor or language exchange partner.*
Although the app will not support adding vocabulary, as in single words separate from sentences, theoretically you could add a "one-word-sentence" if you wished to add a single word to your cards for review. But we would recommend that you switch to full sentences after learning the 625 stand alone words that we have put in the app.
* Note that you'd find those native speakers on another website; we're not supplying them as of yet.