Since my new classroom is dog-themed also, I am just adding to the fun decor that came with me. In going through costumes the other day, I came across this flannel dalmatian costume I'd made my son, Ger, when he was little. So, I brought it to school and put it on a a stuffed doll and sat it in the director's chair - pretty cute, especially since we are approaching Halloween. ( I haven't decided if he will stay after halloween or not, but I think he will.)
This can work for many different classroom themes. Think about your theme and if there are costumes that would easily work into your creative decor. An animal-print theme could have any of the jungle animals costumes to match, like the do-it-yourself lion costume I just saw on Pinterest. A Harry Potter-themed class would be easy to find, buy, borrow, or make one of the characters, muggle or otherwise. Dr Seuss classrooms are big now and that would be fun!
Even if your classroom doesn't give you any ideas for a costume to match your theme, you could dress up a stuffed doll as a mad scientist for the science section, or a colonial girl, or something to match the book you might be reading.
I'd love to hear about your ideas! Your students will notice your imaginative ideas and even come up with their own. My students pull this little dog up into their small groups so he won't be left out......