Hey guys. I decided to make a pre-made png file so your tnt explosions look like fire works, but it's not a mod( I think) so you don't have to worry about lag. Link is here. I'm not sure what photo sharing website to use , but when i find out I'll post some PICTURES. All you have to do is:
1)Open up your minecraft.jar and open the misc folder.
2)Save the png file you just downloaded somewhere easily accessible.
3)Delete the explosion.png in the folder and click-and-drag the downloaded file into the minecraft.jar window(you will need 7-zip or winrar to do this.)