Originally I wasn't going to do a baby shower this pregnancy. It's my third baby (but my partner's first) and we don't really "need" a ton of "stuff". I have been planning since the very beginning to do a motherblessing ceremony tho. But...being my partner's first kid his mom really wants to throw me a baby shower. At first I wasn't sure how I felt about it. Baby showers tend to feel like a lot of pressure to smile and say thank you as you open endless gifts. But the thought behind it is really sweet and I know it means a lot to her so I decided to go along with it. I decided to do a registry at an altnerative/natural baby store online and a local cloth diaper store and to also say that in lieu of gifts, a frozen meal for postpartum would be greatly appreciated. And now I'm kinda getting excited about it.
To answer your questions...
Food...depends on the time of day...munchy finger foods, deli plate, sides, etc usually works well
games...personally i can't stand the silly shower games, which is one of the reasons i didn't totally want a baby shower at first. if they're your thing go for it! but if not, i saw leave it out. spend the time socializing, plan some sort of art activity, have a blessing circle, whatever feels right for you
i'd say minimal decorations if any. maybe a few balloons here and there. but especially if you are doing the leg work, don't stress over decorations. people want to come because they care about you and want to show you a little love, they won't really care if there are decorations are not. and it's definitely not worth overdoing it for a baby shower especially late in pregnancy
men...typically men don't come to a baby shower. but of course, it's about you and that baby bump so if you want men there, invite them! that's my philosophy at least. i'm not necessarily one to follow all of society's rules and norms. if it feels right for me, i do it. so if i want men at my mothering blessing or baby shower they will be there (altho, personally i'm still on the fence on this one)
and for what it's worth...i have never heard of the diaper party thing. sounds kinda silly but also a nice way for your man to get some support/celebration and a great way to have a head start on a diaper stash :)