Is it possible to paste images or tables into string attribute date types?

No, it is not possible. In many applications, the data types String and "Rich Text" are distinctively defined. Usually, String means "plain text" where even formatting is not allowed, let alone supporting images and tables. On the other hands, "Rich Text" usually supports a subset of the HTML or XHTML standard, but the implementation varies across applications. In RDNG, only the "primary text" (or "content") supports images and tables.