Unable to attach files

[Team Twisted]

Hello, 

I have recently created a new forum and when testing the ability to attach files I've encountered an error :

"Please correct the following errors before continuing:

• The type of file that you attached is not allowed. Please remove the attachment or choose a different type.
  
  
• The type of file that you attached is not allowed. Please remove the attachment or choose a different type.
  "

I've tried browsing for solutions using the search however it appears most people must have the back end adjusted by the CreateMyBB team for it to be resolved.

Our forum is for an e-sports racing team and will certainly need the ability to upload .sto files (our car setup files) and .tga / .mip files (paint scheme files).

Our forum address is teamtwisted.createmybb4.com

Please advise.

Thank you!
Chris