Closes #2244

Adding the specific text from the tickets, about image background being white/transparent assuming light color.

chapters/annotations.tex

@@ -1178,6 +1178,8 @@ \section{Annotations for the Graphical User Interface}\doublelabel{annotations-f
 parameter-group (only one image per group is supported). Disabling the
 input field will not disable the image.
 
+The background of the groupImage and any image used in HTML-documentation is recommended to be transparent (intended to be a light color) - or white.
+
 The value of the connectorSizing annotation must be a literal
 \lstinline!false! or \lstinline!true! value {[}\emph{since if the value is an
 expression, the connectorSizing functionality is conditional and this