This member has provided no bio about themself...
Look for the credits for each model that you want to release and contact the authors directly.
Each author can give permission for his own work to be used in other venues, otherwise the answer is no, you may not use it without permission.
Just a quick suggestion here:
You could start with a more elaborate concept if you have some dedicated modellers/animators for a quick sequence.
Seeing as your logo has fire and ice on it, I'd start with a close up on a middle point of the black screen and have an icey freezing over effect growing in, forming the blue part of the logo as the camera zooms out. Same applies for the fire part. Do it at the same time and then you have a cool simple intro.
Youre suposed to select JOIN on the Play Menu. The profile menu is bugged and will be fixed in the upcoming patch.