How do you proceed with copyright infringement?

Near two weeks ago, I released a mod (or skin) for the popular Flappy Bird game with an original doge character asset. I let the the people of reddit use and mod it for personal use as long as proper credits were attributed, not for commercial purposes. Redditors began contributing to the mod and we had a nice thing going.

Dong, the Flappy Bird creator, was a fan:

  https://twitter.com/cheeyoon/status/431960771983970304

It could have been on the next update as an easter egg had he not taken it down lol.

Lo and behold I see this Dumpy Doge game (top 10!), along with a few others on the Google Play store, against my terms. A few reviewers, including Pewdiepie, have also promoted the app(s) which is a bit upsetting.

Proof of original ownership:

  http://www.reddit.com/r/jailbreak/comments/1x2csr/remix_my_custom_flappy_bird_mod/
  http://cheeyoon.com/post/75677698649/flappy-doge
  http://imgur.com/a/1uKOr
  https://vimeo.com/85904559

I've filed for DMCA takedown on various sites across the web and through AppStore and Google Play. Any advice on how else to proceed? First experience with this