I don't have the pictures of the 20 kopeck coins, the rarer variety of that date is just so rare. I'm not aware of any varieties of the 15 kopecks 1974, it just happens to be quite a scarce coin. There are some interesting varieties on 3, 2 and 1 kopeck coins too, but I suppose they aren't as well known and highly priced as the higher denominations, while some of them are equally scarce.
The coins in mint sets aren't usually as highly prized as the regular uncirculated coins. The mint sets are relatively easy to get, just try to get a regular circulation issue of the 15 kopecks of that date...