Going with a dark navy velvet jacket, black tuxedo trousers, white shirt. Which color bowtie? Have black on standby but was thinking something textured? Also, what color velvet loafers- black or dark navy?
Seems like you're putting together a nice rig. Stay with a black bow tie. It's conventional to have it close in texture to the facings on your lapels of your jacket, usually either satin or grosgrain. If your jacket doesn't have facings then it's your choice.
I was in Aldo recently and saw plain velvet slip ons in both navy and black for about $125 IIRC. Either will work well with your jacket. I think Steve Madden might sell variations too for a similar price. I've seen the Del Toro ones mentioned above but I think they are very expensive for shoes you will wear once a year.
I have a similar rig to what you describe and got suede loafers from Florsheim instead of velvet slippers as I thought I'd get a bit more mileage out of them. I think they still are available in nevy and black suede so you might want to think about them. Good luck!