The funerals that I have attended in Scotland have been fairly standard affairs, with no tartan around, except on the mourners. It's personal choice though, so no reason not to have the coffin decked in tartan if that's what the family want. No reason not to be buried in your kilt, but I haven't heard of it - probably because most kilt wearers over here will only own one or two kilts, and they tend to be inherited by the sons. There's something special about wearing a kilt that's a couple of generations old & still going strong.