There's a ton of things you can do if you don't care about form or technique or any of that.
Start with just working towards hitting the bag consistently for a three minute round - or multiple three minute rounds. This is typically harder than you think.
Once you can do that, work in intervals: go all out, throwing nonstop punches (or kicks or whatever) for 20 seconds out of each minute. Then go back to a slower punch rate until the next interval.
Or do 5 one-minute rounds of nonstop 1-2's, and do 10 pushups during the 30-second breaks between rounds.
Or do a three-minute round, then do jumping jacks during the one-minute break, then go do another round on the bag.
You can come up with a pretty endless amount of things.
Just don't think you're getting more than what you are - a great workout focusing on explosive strength and muscular endurance. If you want to throw "solid" kicks or punches, you should work with a trainer, at least for a little in the beginning.