You can use Trello. It satisfies all the requirements that you have specified. Users can add items which may include text, pictures etc. They can comment and vote on the items added to the List.
In addition to this, you can add a
Check list , etc. to the added list items. Trello is a very useful platform for brain storming and working together as a group.
An example of a Trello Board, with the voting feature can be seen here. It is maintained by Nick Craver, Site Reliability Engineer at Stack Exchange.
Please note that the cards are not ordered by votes. This feature is not supported yet. However if you wish see the cards in the decreasing order of their votes, you may use the Ultimello chrome extension.
This will let you see the cards that have more number of votes at the top.