Sell retweets (Fiverr, etc), sell your account, tweet affiliate links, retweet affiliate links your post from other alternate accounts (to not alienate your 60k followers so much), change your bio link to an affiliate offer or Landing page link... There are sites that let you create image galleries that are monetized- they appear to be popular among large accounts but I don't know how much money they are getting. Browse through some large accounts and you'll see there's lots of subtle monetizing going on all over.
Does your account cater to a certain niche?