I'm personally not a fan of coed showers but if you're going to go that route, a BBQ would be nice.
Neutral themes include jungle, sea life, sweets/candy/dessert-themed, farm animals, Dr. Suess.
Even though some people are not fan of alcohol at baby showers I'm okay with it and I think if the person pregnant is okay with it then you are good to go.
We knew we were having a girl so our colours were grey, yellow, and pink but I agree with neutral themes and colors like yellow, green, brown, grey will work well.
We also had games that both men and women would enjoy. My friends and family are big drinkers so we did beer in the baby bottle and whoever finished it first won a prize. We also did the guess the chocolate bar in the diaper and the game where everyone wore a clothes pin, and if you said baby whoever heard you say it or made you say it took your pin.
Whoever had the most pins wins.