telerik:ScreenTip.Description="Cut the selection from the document and put it on the Clipboard."
Please mind that we have predefined size for LargeImage -- 32x32px and SmallImage -- 16x16px. Whether you need bigger size (I saw that your Canvas is 76x76px) you can set the IsAutoSize property of the RadRibbonButton to False. This will automatically make the button's predefined image size NaN -- it will render as big as its dimensions are. Please note that RibbonView has strict Height and this might cause your image to be clipped (if the size of the image is bigger than the Height of the control). In this case you might change the default size with your custom one by setting the ContentHeight property as stated in our documentation.
I hope this information helps.
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items