I do a lot of shooting at events of this nature.
Pretty good work with a wide-angle, nice use of perspective distortion in many of them.
It's tough to get a "clean" background in this sort of setting. If the subjects will cooperate, I personally prefer to stand a little farther away and use a longer focal length, to minimize background clutter ... but sometimes that's just not practical. Depending on the con and location, you can sometimes find a little out-of-the-way corner to set up a light or two, and then ask people to "step into your office" for a more controlled portrait ... I guess that's what you were doing with your other studio, though.
Inside the dealer's room (#8) is always a tough place to shoot. Usually you have fluorescents or sodium-vapor lights high overhead, coupled with dense crowds, making for a very tough shooting situation. Not bad, though at web size her face and lashes seem distractingly oversharpened.
I'm generally not a fan of pure B&W images for cosplay & costumes; the vibrant colors are often a very significant part of the overall look, and you lose something when you desaturate. Sometimes I'll do a very stylized B&W conversion, or a partial desaturation, but usually I'll add at least a little bit of color back in with split toning or a color overlay.