Some are quite handsome. Some are unattractive. Some are ideal for spring and summer, while others are best worn during fall and winter. Some of the ones in my closet are fairly staid and conservative, while others are lighthearted and whimsical. I have worn paisley ties to weddings, to court, and to lunch. I've never worn one to a funeral (although I have seen black-on-black ties which probably wouldn't be the worst choice for a funeral). I'm especially fond of paisley bow ties. I think that too many people assume that a paisley tie has to be a riot of color, and frankly rather garish. In fact, a paisley tie can be extremely refined and elegant. Depending on the precise situation, a paisley or plaid tie can do a fine job of keeping a solid colored suit and solid shirt from seeming too static. A paisley or plaid tie can also take a suit and shirt combination from "conservative business" attire, to more relaxed social attire, quite nicely. As I am thousands of miles from Scotland, I do not care in the slightest whether my plaid tie's colors "belong" to any particular clan. I never match my plaid socks to my plaid tie. Come Christmas, a red and green wool paisley bowtie beats a necktie with little Santas/reindeer/sleds/Christmas trees on it, every time.
If you could narrow down your question a little, and ask a specific question about paisleys and plaids, or even a question about a specific tie, I might be able to give you a more focused answer.