I paint in oil on canvas board. I can work to specific size requirements but the usual size is approx 18" by 13". I used to paint on stretched canvas but various postal services seem to enjoy bending the art and trying their best to damage it.
Below are a couple of examples. The Reverse Flash piece was on a bigger board but as a single figure with a basic background, something like this would be about £1000. The Spider-Man one is an oversized piece, about 70cm square and is a good example of a crazy amount of figures. It cost £2250 and the SubMariner is an example of one at the 18" by 13", something like that, with one figure and a simple background would be £750.
I enjoy doing these, especially by artists who's work I like. Straight price, $300 (about £180 or so) for the linework ones. That includes me drawing in the logo, price etc. Unless you don't want it on...The full tonal pieces are $400 (£250), they're obviously more time consuming, but they look pretty nice. Cover recreations are approximately regular comic art size 15" by 11"
Prices are £80 for an 11" by 17" (or A3 depending on where you live) and £40 for one half the size (A4)
Get in touch if you'd like a pre-con commission sketch doing before the convention itself so I have time to fit it into my schedule/put it on my list. They're basically copic marker, pencil and ink and are finished/detailed convention sketches. I'd like to say they're similar to what Adam Hughes (did) or Copiel does for pre-con commission sketches...but they're clearly not as good as the sketches they do (And the price reflects that!) They do look quite nice though!
Also, I'm adding sketches with colour, by that I mean a tonal copic one but with some watercolour added in. Not really bright, but pretty nice. I'll post examples and prices as soon as I've experimented a little and figured it all out. Just wanted to mention it!
Over the last year, well since the Film and Comic con in July, I've added in film and TV sketches too. Some examples of ones done for previous conventions...I'll post more soon, these are the only ones I scanned/managed to find on the internet so far!
I do a fair bit of this kind of work. £250/ $400 for something like the pieces below.
I occasionally get asked to do pencil pieces too, these would be on a price per job, but about £200 for a fully rendered one at traditional comic book art sizes 15" by 12"
If you'd like to be added to my commission list then email.