Teacakes in a tea-room play a secondary role as a rule. Tea is regarded as the main part, and teacakes are considered not to damage the taste of the tea. The use of the ingredients which have a strong aroma should be avoided. Yuzu(which has a slight lemon fragrance)or something similar would be acceptable.
It is also important to make confectionery that puts importance on a sense of the season. Some confectionery can express this sense by ingredients, others can express this sense by shapes or colors.
As with teacakes, size is also important. Especially in a tea ceremony, confectionery served is not very big.
Confectionery that you can eat in two bites is favorable.
Also, confectionery that is hard to eat should be avoided.
It is also important to dish up teacakes into containers with beautiful shapes. The color and shape of cake tray need to be chosen with much care so it harmonizes with the confectionery. You should choose one that complements the confectionery.