Botanical relates to plants and having items like framed fern or flower specimens look great in a kitchen because of the natural link. They provide wonderful colour, especially if grouped together.
Victorian Museums, such as the Natural History Museum in London, has built up over many years great collections of insect examples for both study and scientific purposes. Those who study insects are called Entomologists (a branch of Zoology, the study of animals). A fascinating and popular hobby for many, they are great for including in your Cabinet of Curiosities or for just making interesting unusual decorative ojects. Cased butterflies in domes are a particular favourite at the moment.