Are there any safety guidelines for mixing sulfate with chloride?
Overall, always wear disposable gloves, goggles, and a dust mask.  Add a lab coat, smock, or apron so as not to contaminate your clothing.  Avoid skin contact, don't ingest and don't inhale (this includes the dust).

Manganese heptoxide is a special case with concentrated sulfuric acid.  Avoid mixing strong oxidizers (permanganate, chromate/dichromate, perchlorate) with organics.  NEVER screw around with chlorate salts.  They are powerful oxidizers with very low kinetic barriers.  Finely divided metals (especially titanium) can go to white-hot burning in open air.  Titanium burns under air, carbon dioxide, nitrogen, water...

Palladium is a heavy metal, poison and tissue corrodant.  A microgram of tellurium by any contact gives "tellurium breath" 

Local contact with chromates can cause ulceration.  Neodymium gives you purples, cerium yellow to orange.  I seem to remember that cobalt blue (cobalt aluminate after firing) in tin oxide applied to white ware gives bubblegum purple.

Tin Glazing

Gold via the Purple of Cassius is very nice.

Here's a pretty!  Suppose you mixed clay with hollow glass microbubbles, then fired.  Would the clay foam to an interesting surface or whole body?  This is the stuff, sold generally as lightweight resin filler, including hobby stores.  Most prices are outrageous when sold by volume.  Density of 3M Scotchlite K20 is 0.2 g/cm^3.  Goggles and dust mask.  Be careful or the stuff goes everywhere.

http://www.aircraftspruce.com/catalog/cmpages/bubbles.php 
Good price. 
http://solutions.3m.com/wps/portal/3M/en_US/Energy-Advanced/Materials/Product/?N=5002440+7570097&amp;rt=r3