TIFF, BMP and PSD files can be a bit of a pain sometimes because they are so big when it comes to storage. PNG files are much smaller so I think it would be really good if Zbrush had PNG support for the simple textures (IE ones that are not 16 bit). Saving as PNG would just save time for me to convert them later. I realise that importing PNG may be a bit of a problem but PNG files could be automatically converted by Zbrush upon importing.
What say you, Pixologic?
Cheers,
Revanto 
PNG – like JPG – is a compressed file format. Any time you compress a graphics file, you lose quality.
ZBrush does allow import of JPG files.
It does not write such files for the simple reason that good image compression is a very visceral thing. You the artist need to look at the image at various compression qualities to determine how much you’re willing to sacrifice for a smaller file size. PNG is further complicated by offering a lot of options that aren’t even available for JPG. So such compression is best accomplished through a dedicated image editing program such as Photoshop or Fireworks where you can actually see the various options and compare them before you commit to one.
In short, ZBrush is designed to create the highest quality output possible. If you want to muck it up by using a compressed file format, well that’s your business. 
Well, you don’t have to say it like that, you big meanie 
Revanto
PNG support would simply rule!
Yes, PNG is compressed. BUT: it’s a lossless compression! So no quality is lost at all. Plus PNGs support 16bits color depth, too!
http://en.wikipedia.org/wiki/Png <- !!!
So please please with sugar on top please support it in the next version!
THX!
tiff can be compressed too (also lossless). I would vote for better tiff support. The simple truth of the matter is that pixologic could support all of this and more if they would integrate something like imagemagick, which can be done legally for free.
However, I would vote for, “get it done,” over adding more image file formats without hesitation.
Heres one more request for PNG support!
I agree… I use almost png for my works. Really cool format.