For real estate, each region is free to define their own valuation rules. In Zurich, either 70% of the previous transaction value is used, or a conservative value based on size and location, whichever is higher. This value is often also the basis for the self-rent-tax. (In Switzerland, the amount you could earn by renting out a self-inhabited property is taxed as income. Not doing so would give homeowners an unfair advantage in comparison to renters.) Paintings and jewelry are only taxed if they make an unusually high share of your wealth, i.e. if you are a collector. Again, the exact guidelines vary depending on where you live.

Here are the official guidelines for valuing real estate in Zurich (in German): http://www.steueramt.zh.ch/internet/finanzdirektion/ksta/de/... Note that you do not have to apply these rules yourself. Instead, the local tax office performs the calculation and notifies you about the result. If you disagree, this result can be contested, but generally, you do not need to familiarize yourself with all the details.

Don't know about Switzerland, but in the Netherlands where there's also a wealth (or rather, net worth) tax, most property held for personal consumption (art, jewelry, cars, boats) are exempt. Their value in the aggregate is relatively low (compared to real estate and financial property), so the lawmakers decided it was not worth the hassle to tax those.

Real estate is taxed separately, and municipalities run yearly appraisals. But I think that's pretty routine in most developed countries?