How can i make steam skin?

You mean background? Buy one on the steam market or craft a game badge to earn one. Then you can change it by editing your profile.

U can only change ur profile picture and for steam skin(background image, it will be from creating badges or buy from market....)

Check steam options, you can change your steam skin somewhere after downloading from web ofc :P I personally use blood skin

Develop a game, pass Greenlight,draw cards and backgrounds for it, craft a badge for your game, get the background,"equip" it, PROFIT!

Thats not what i mean xD I want to make one so i have that picture on steam

Steam skin != profile background.

online tutorials?

Your wallpaper is cool but this one is even better :

View attached image.

It's not actually possible to make a custom profile background for the steam client, but this works for accessing steam through browsers, and let's others who have it installed see your custom background. BTW, google works wonders for finding this kind of stuff out.