I want to make a flame particle texture , the rezolution is 128x128 right? and may sound weird but what format should I use , .png?

While I'm not sure about the resolution, I think that they can be in any of the usual texture formats (.BMP .GIF .JPG .PNG .TGA .TIF).

Yes, the correct size is 128x128. The formats were mentioned above.

you cant use .PNG right now(i dont know.. but when i use .PNG the image cannot uploaded) i think you can use .JPG or .GIF

vman : It works for me

kaiser : thanks , but I've seen that it still looks the same if you use 256 or 512

It resizes itself once you upload, if it's bigger than 128.

Go for 128x128... Make the background transparent for a more on-the-point effect.