Busycal allows you to add graphics from your desktop or the web to your calendar.
You may drag a graphic into the calendar to create a floating graphic attached to a date.
To select a graphic, hold down the Option key and click the graphic. Handles will appear that allow you to move and resize the graphic, or delete it by hitting the backspace key.
You may minimize a graphic by selecting it and choosing Minimize from the Edit menu or typing Command-/. The graphic will be minimized and displayed in the date header area. Clicking the minimized graphic will maximize it to its full size.
You can also drag a graphic onto an event and the graphic will be attached to that event and appear in the date header.
You can control the transparency of a graphic in the info panel by dragging the opacity slider.
Below are some some sample graphics that you can drag-n-drop into BusyCal.
The sample graphics above were found on interfaceLIFT