Im in the process of setting up a bench for all my reloading/tinkering/gunsmithing and I want to put a vise on it. I already have a bench vise that I could use but was wondering what you guys use to pad the sides. I know I can buy a block for my ar upper and lower but what if I want to put a shotgun receiver in it? I will need something to pad the sides to put them in it. Just wanted to know what you guys use. Pics are always helpful. Thanks guys.

You can usually find magnetic polyurethane vise jaws that just stick to the existing jaws or you can use pieces of carpet. Go to a carpet store and get a couple of the self stick carpet tiles. They have a very dense backing but are soft enough not to damage a receiver. Cut it just a hair bigger than the vise jaws and stick it to them, toss a clean rag over them and away you go.

For small parts get a Versa-vise. They have smooth plastic jaws.
For your big Wilton, get some polyurethane stick ons

I just use shop towels or scrap wood.

For quick jobs, cut some some scrap leather to fit the size of the jaws and rubber cement in place.

Google magnetic vise jaw pads or vise jaw caps

This. I cut up old leather belts.

workbench thread

Above shows a number of vises.  I use a number of inserts on my metal vise depending on the application.  Polyeurethane, magnetic wood inserts, metal bending inserts, barrel inserts, etc.  

If you're near Charlotte you're welcome to come over and take a look at my shop.

The Gunsmith I associate with has used these from Brownells day in and day out for decades:

http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/vises-accessories/vise-jaws/elastomer-pad-for-multi-vise--prod22186.aspx
They're a little on the expensive side, but they do work very well.
On the cheap, you could buy a Truck Mud Flap from any place that sells Commercial Truck parts for as little as $9.00 cut a couple sections, then glue them to a piece of angle Iron.

On a tangent: Buy a good vise, and I mean a really good American made vise that will serve you well the rest of your life. Secondly when you do, find a Shop that supplies Metal and buy at lease a 1/2" plate, preferable 5/8" or even 3/4" then drill the plate for the vise and bench bolts, additionally for a good many benches it's best that you match the plate holes to bolt through the bench, sandwiching the bench top.
On another tangent while you're buying plates, have one cut approximately 8"x10" then drill & tap holes to mount your reloading press; I have one with multiple holes and sizes to accept everything from a Pro-1000 to the .50BMG set up (the .50 puts a LOT of torque on the bench top and bolts)
A chunk of 5/8" mild steel plate isn't all that expensive, neither are a couple of drill bits, and taps, however a Drill press IS a must!

Just buy a quality machinist vice and all of the inserts become unnecessary. Add some v-blocks and you'll have 99% of your fixturing requirements covered.