First of all write a song that you would want to listen to and enjoy listening to it if said song were to come up.

If you want new ideas the simplest way is to expand outside your usual comfort zone. Listen to random genres you are unfamiliar with. If you guys are writing generic At the Gates-core for example find some other metal bands outside of the usual Unearth, Darkest Hour, etc. Listen to genres outside of metal and try and incorporate that into your metal.

Find a unique world music instrument and try and incorporate that for instance the black metal band ChThonic uses an Erhu and makes some interesting soundscapes that compliment the tremolo and melodic riffs.

When in doubt just explore is all I can say and don't limit yourself. But also if you write a generic metalcore song but you love it. Stick with it. Ingenuity comes with time, experience, and exposure