Yes, their reverse side designs are different for each country, but all are valid all across the Euro area - remember that Sweden, Denmark and United Kingdom are members of the EU, but are not using the Euro (this also goes for most of the new EU members, except Cyprus, Slovakia and Slovenia).
Europe has over 50 countries and most have their own currencies. 17 countries use the Euro. Within each country that uses the Euro the notes are the same but coins can be different.
If by 'bills' you mean banknotes, banknotes are printed. Coins are minted. Each country which is part of the Euro prints its own notes and mints its own coins. The coins all have a different designs on the back for each country. The notes are all identical, but the first character of the serial number indicates which country printed it.
The symbols on the coins are fairly irrelevant and all euro coins are accepted in all member states. There is no monitoring of national sides. Although all Euro notes are essentially the same there are country specific symbols or pictures printed on them
Each country has a different version, although all of the coins must be the same size, weight, and color. The reverse side of all coins of a given denomination are identical. Only the obverse ("national") side will display a design unique to the issuing country. (see the two related links below)
Many websites have Euro coins for sale in their inventory. Two websites that sell the Euro coin are eBay, and Etsy. Each website has their own variations of coins and prices.
As of the 1st of January 2014, 18 countries in the European Union use the Euro as their currency. Each country has a slightly different set of coins to reflect the countries history, with one side being different. The other side is the same. The notes are all the same in all countries.
Each country that has the euro has its own type of euro coin, with one side having an emblem of that country and the other side being the same in all countries. However all euro coins can be used in any country that uses the euro. So one side of the French euro is the same as the Germany and Italy euros, and the other side is different on each. They are the same in that they can be used in any of those countries and any other euro country. See the link below for the designs one side of the first 13 countries that used the euro. The other link shows the other side which is the same in all countries. Some countries have also minted some special ones, with one side different.
Yes, any country in the Eurozone will accept euro coins from any other country. The euro is a single currency of 15 countries in the EU and is under the control of a single independent origination, the European Central Bank. All banknotes are the same, however each country can mint its own coins (under control of the ECB). The coins are all of a standard weight, shape, and style, and have a shared standard front design. The back of the coins are dependent on the country of issue. The coins are acceptable anywhere in the Eurozone. A number of European microstates are also permitted to mint a small number of their own coins. Monaco and the Vatican City are examples of this. Due to their limited numbers these coins are usually highly sought after by collectors and can often be worth more than their face value. Allowing each country to mint coins with a national side helps to spread the culture of all countries in the Eurozone. Seeing an interesting and unusual design on a coin will often encourage people to learn more about their neighbors.
The 5 euro cent coin is copper in color, about the same diameter as an American nickel (but slightly thinner), with the number 5 and the words "euro cent" above a map of Europe on one side, and the specific country's design on the other. Each eurozone country has its own set of designs for all euro coins.
Euro coin denominations are €1, €2, and 50, 20, 10, 5, 2, 1 cents. Each country in the Eurozone can mint its own coins. All coins have a common size, shape and common side. The design on the reverse of the coin is chosen by the country of issue. As well as each country minting its own coins, a number of microstates such as Monaco have agreements with the European Central Bank to mint their own coins. Some countries have a design for each denomination of coin, others choose three designs and apply them to the range of denominations. Some countries such as Belgium or Ireland choose one design and use it on all their coins. Finland does not issue 1 and 2 cent coins at all. In addition to this each country may issue a special €2 commemorative coin every year. Though not every country chooses to do so every year. The Vatican City coins which feature the current Pope, had to re issue all of its coins after the death of John Paul II. The new coins feature the new Pope Benedict XVI. It should also be noted that minor changes have been made to the common sides of the coins since they where first introduced. The answer to your question all depends on how far you wish to go on "different". In any case, there are a lot.
The euro is a shared currency used everywhere within the "Eurozone" countries. It doesn't belong to any specific one of them. Euro coins and bills are completely interchangeable no matter where you are or which country issued them. All euro bills are identical, so it's not possible for the casual user to tell which country issued a particular bill. The only difference between the Eurozone countries is that each one puts its own designs on the back of its euro coins. The front (obverse) side is identical for each denomination no matter where they're made.
The Euro is the same for all countries that use it, though one side of the coin is different in each country. All the notes are the same for all countries. You can still use those different coins in any of the countries that use the Euro. Not all countries in Europe use the Euro. There are over 50 countries in Europe. 28 of them are members of an organisation called the European Union. 18 of those 28 countries use the Euro as their currency.