<span style='font-family:Comic Sans MS'>.png is the best u should NEVER save as a .gif unless it's an animation start reading where it says ".APNG Support" <a href=\'http://www.gamerenders.com/forum/index.php?showtopic=211644\' target=\'_blank\'>http://www.gamerenders.com/forum/index.php?showtopic=211644</a></span>
He said it all. You can use TIFF and PNG as they are the best formats in images and cannot be beaten at quality. I prefer to use .PNG 99% for still images and 1% JPG for useless images. For animation file I always use .GIF as its your only option
if u have Photoshop then u can save it as a .jpg BUT keep the same quality as a .png by goin to Save For Web and then setting the jpeg quality all the way up
PNG is fairly lossless compression compared to Jpegs, so I use PNG. Used to use TGA files years ago, but for them to hold an alpha channel reduces them to 16bit images...bleh.
Depends on what i'm doing, if the file has to be small then i use .jpeg, if it can be any size then i use .png, and if i want animation i use .gif