OK; In my opinion, you can only use 4 items in spkToolbar (spkLargeButton, spkSmallButton, spkCheckButton, spkRadioButton). However, it is absolutely necessary to have the following components (spkImage, spkCombobox, spkLabel). Because I want to use this excellent toolbar in an application. For this reason I want to request a new feature. Does it make sense to you?
The problem with SpkToolbar is that the components which you add in design mode directly inherit from the very elemental TComponent, i.e. every feature that we know from the LCL has been added manually - I don't know why the author decided to go this hard way. Therefore it is not straightforward to add any new components to SpkToolbar - I did it with the Checkbox and the RadioButton, but this was really a hard learning curve.
And the original author who donated this component to the community never reappeared again. So, there's nobody to ask...
On the other hand, adding a image should be feasible. When I have some spare time I can try, but I cannot promise that it will be soon. What do you need it for? I've never seen standalone images in a ribbon.
A label only makes sense if there is something to which the label can be attached. But all controls available so far do not need a label. So, adding a label at the moment does not make much sense. Or do you want a label just to display some text information (e.g. display of current time)?
A combobox will be rather difficult - can't you use a Smallbutton with kind bkDropdown or bkButtonDropDown?