Have just been trying to understand the opening verse of Diwan-e-Ghalib. Finally after looking at few of the books and translations, it is making some sense to me. So here is what I understood of it.

Poets generally start their work by remembering the God and praising him for creating this world. Waris Shah opens his epic qissa Heer with:

awal hamd khuda da vird keeje,
ishq kita su jag da mool miyan

First of all let us acknowledge God, who has made love the worth of the world, Sir – Translation from Wiki

Ghalib also does the same but bit differently. He does acknowledge that this universe was created by God but doesn’t praise him for this. He rather takes a shot at God and complaints about the pain and sufferings humans go through in this world. The complete verse is:

naqsh faryaadi hai kis ki shokhi-e-tahreer ka,
kaagzi hai pairahan har paikar-e-tasveer ka

First few word meanings:

naqsh – a painting or portrait
faryaad – complaint or plea so faryaadi – the one who is complaining
shokhi – mischief
tahreer – handwriting
kaagzi – made of paper
pairahan – clothes
paikar – face, form, appearance

Before we get in to the explanation it is important to understand the importance of kaagzi pairahan (clothes made of paper). It has its roots in old Persian tradition where the complainants would go to their kings wearing clothes made of paper. It was considered a symbol of humility.

In the first line Ghalib says “who did the mischief of creating this universe ? You ! right ?” So he does acknowlge that everything has been created by God. But he sees everyone (all humans) as faryaadi and to who we are complaining ? of course God. So he relates the condition of humans to someone who is there in a king’s court with his faryaad. Here we are the complainants and God is the king. He questions the very creation of such world where there is so much of suffering and everyone seems to be doing a faryaad in the king’s (God) court. What was the need to create such a world ?

Here and here are some links discussing it in much more detail.