Say I wanted to make a free (+no ads etc.) app which is essentially a trading card game but the cards consist of characters designed to be similar to ones from other apps. For example, one card would be a different coloured 'Angry Bird' styled bird.
Is creating this art in my free trading card app considered trademark/IP infringement?
I.e. creating new concept art (similar styled) but not using actual characters by Angry Birds, like this:
If so, would I need to get license/permission from each app I wanted to include?