@freezyfrog: It would be easier to answer if I knew what kind of stuff you wanted to add but for stuff that can be added basically solicits (in italics), plot summaries (summaries not panel by panel descriptions or in-depth), unordered lists for story/chapter titles or contents (no page numbers though), cover info tables, publish dates if more then one (TPB & HC, print & digital), notes of interest as long as they are not redundant to whats listed in other sections like associations, 1st appearances for characters can be added but it is outdated since 1st appearances show on character pages, that's about it I guess. The order I listed all those things in is also the order in which they should be presented in the description from top to bottom, what gets included depends on the issue though and you only have to add what you feel comfortable adding.
Note: Also for issue names there is the name field where story titles go but generally if an issue has more then three story titles or it uses long story titles they should be moved from the field for names into the unordered list for story titles. Reason being is cause to many titles in that field looks bad when looking at issue grids and because a shortened version gets added to the URL link so it's best to keep the field shorter and use the unordered list.
Note: All the above stuff needs to be in the main description which is the second text box where you get the extra formatting tools, that top box is called the deck and it is meant to be a summary of the entire page (it has a text limit and can't be formatted) but decks are rarely needed for issues and volumes, they are more important on other page types so for issues/volumes they should be left empty.