Raw beef and raw tuna have some similarity in terms of color and texture. As a result, it was easier to be accepted by Westerners if tartar was made with raw tuna instead of beef and call it tuna tartar. Carpaccio is another very common Western adaptation of sashimi. Instead of using thinly sliced raw beef, you use thinly sliced raw fish, especially tuna. You can also make carpaccio using white meat fish such as Japanese snapper or tai 鯛, halibut or even scallops. I understand that, now in Japan, carpaccios of raw fish are very popular.
kinshiran 金糸卵 or golden egg thread, roasted white sesame seeds and chopped chives. Again, you could use any combination of garnish here. This will give a bit different twist to tuna sashimi. Like beef carpaccio, this could go well with red wine or sake. We had this with 2007 Joseph Phelps Cabernet which we just received. "Shime" 締め or 〆, the last dish (usually starch) was Uni-Ikura donburi 雲丹いくら丼 tonight so we switched to cold sake, what a decadent night.