Mercht takes cases of copyright and trademark infringement very seriously. If you believe a campaign on the site, whether currently running or previously available, infringes on any of your Intellectual Property Rights please contact us at firstname.lastname@example.org
Definitely not cool. You can only upload designs to Mercht that you have created yourself, or have express (written) permission from the creator that you are able to use the artwork.
Uploading or creating a replica of someone else's intellectual property can result in action being taken against you, the cancellation of the infringing campaign, and the suspension of your Mercht account.
However, your use of the existing work must also be fair - if your work commercially competes with, or would impact upon the commercial exploitation of, the existing work, or if the amount of the existing work you have used is unreasonable, your use of the existing work will not be "fair" - and as such you would not be able to claim that your work is a genuine parody.