Keyboard accessories will vary according to what style of keyboard you may have and also how your keyboard is used. Assuming that your keyboard is transportable and that you may be using it for public performances, then the first two things to consider are a gig bag (or flight case) and keyboard stand.
The gig-bag or hard case will protect the instrument in transit and provide a means of storage when not in use. A secondary consideration is a keyboard stand to allow a comfortable playing stance, however if you prefer to play your keyboard when sat down, then you'll need to think about a suitable stool or chair - again you should ensure that it allows you to be comfortable when playing.
Other accessories include a damper/sustain pedal for dynamic expression and also a volume or expression pedal for level adjustment during the performance. If your keyboard is likely to be connected to other sound modules or keyboards via MIDI then you may wish to contemplate a MIDI patch bay or switchbox along with all of the relevant 5 Pin DIN MIDI cables.
