Tips for accompanying vocal warmups

I am the assistant accompanist for a local community choir. I've been accompanying small choirs (think church choirs, high school choirs, etc) for most of my life. But I've always struggled with playing warmups in a way that feels effective.

The collaborative pianist for the choir is amazing, and he adds chords and other flare to the bass line that makes the warmups feel more natural and like we're actually singing. Our conductor tends to throw brand new warmups in the mix every so often, and the pianist is able to come up with a working bass line after two or three rounds of the warmup.

I don't tend to be great with creating music or harmonies on my own but would like tips if anyone has any for adding more flair and musical interest to warmups. It doesn't seem like it should be a big deal, but I've seen noticeable differences in the way I warmup vocally when people just pluck out the warmup notes vs add something to make them more musical. Thanks!