In ismellike's tutorial: http://mcdzienny.cba.pl/viewtopic.php?f=17&t=1861&hilit=texture
He give's a link to the website where you upload you textures and get the ID, but now the website will not work any more... I'm not sure if it's just for me so here's the link: http://files.minecraft.org/upload.php
Is there another way?