???? Liver of sulphur and pickle are used for two completely different things.
Liver of sulphur is used to oxidize sterling silver (i.e. tarnish it); generally, it's used to emphasize recessed designs (Bali beads, for instance). If you don't want to use liver of sulphur (it does kinda stink!), there are other chemical products such as Silver Black available but that turns the silver totally black and doesn't allow you to play with colours the was LOS does. If you want a natural alternative to LOS, do an advanced search of this forum for "egg" - there are been TONS of posts on this in the past few months.
Now, if you want to clean up your piece after soldering, then you're talking about pickle. Pickle is a mild acidic solution that removes any remaining flux gunk after you've soldered. In my experience, pickle will also remove MILD discolouration. However, if you've truly firescaled your silver, then pickle won't help. I accidentally got bleach on a silver bracelet and the only thing that removed the resulting black stain from the deep recesses was a 20 minute soak in hot pickle. (Pickle works faster if it's hot.)
Commercial pickle is available from any jeweller's supply store - Sparex is the brand that comes to mind. PH Down is a great substitute - many think it's superior to Sparex and it's definitely cheaper. PH Down is available anywhere pool and spa supplies are sold. If you want to go natural, I've heard of people using vinegar or lemon juice but I suspect that they'd take longer to work than Sparex or PH Down.
HTH
PS - I'm talking about STERLING SILVER here. If you're using a different metal, then none of this may apply.