|Whilst I don't have first hand experience with this as such, I AM also into sewing and feel qualified to give you an educated guess here.
I'd say go for it! You are right, the velvet with its light-swallowing qualities shouldn't show a seam up very much at all.
To hide it even more, I would do this:
Sew the two pieces together.
Finger press the seam allowance apart, but don't iron it (you would only emphasize the seam).
Use a toothbrush to tease a few more fibres out of the seam, the ones that are bent over and stuck under the cotton.
Now use a wider, softer brush to cover up your toothbrush tracks.
The rest of it (random gozillas etc) can always be photoshopped away, right? ;-)