you can't, maybe with a sp voucher, you can find it at centropolis, but then you're not sure it will be fair

You offer a cheap item and can add sP in the box below. It's the best way, as there is a daily limit fo vouchers.

SP vouchers don't work because you can only exchange like, 6 a day, and most art/graphics is more than that.

The most common way to do it is People set up a junk trade and the customer offers the amount of sP they owed.

or do the same in trades... theres a box where u can write the amount of sp in it

Also some poeple get a bunch of a really cheap item and then put it in a shop and price it whatever the price for their art is and then have people buy the apropiate item from the shop.