Simple Picture to question....

How can i detail this pic with gimp?

Open it in GIMP and apply some filter over it.

And what filter ?

All of them.

Don’t filter it. Just open it up in GIMP and fiddle with some stuff until you think the picture looks better, that’s what I do.

Don’t encourage him to do that, filters all the way.

I like the atmosphere

I’m sorry, but it looks like the guy with the shotgun has a wedgie.

one of them is scratching his butt!

As hilarious as the “apply erry filter” advice is, don’t. Your posing needs serious work. Don’t even TRY to edit until you get that squared away.

Not that great.