You may have a common or descriptive word as part of the trademark, but doing so weakens the mark. You will only be able to trademark the mark as a whole, including, as you note, design, font, illustrations, etc., and will not be able to have a trademark  just in the words. Because the mark  will be more  narrowly drawn in that sense, it will be easier for someone else to come up with a similar--but not identical--mark, differentiating it only by some typographic  or design elements.