Hints for your updated, clarified question (from NOT an expert)
Considering your updated question, there exists a documentation-page on Drupal.org on attaching images to nodes:
But, perhaps easier to start off, is to read some answers posted to identical / very similar questions, here on StackExchange:
Having referred to these, I would like to add that I would intuitively enable pictures in comments, and let people post the pictures in to the comments; but I don't know if that's what you're looking for.
If you would choose them to use the comments: after having enabled comments to include pictures, one can disable unneeded fields, similarly to the method described below, via
- Structure >> Content Type >> Content type >> Comment fields.
- Structure >> Content Type >> Content type >> Comment display.
For further fine-tuning of the display of the comments, the module Views is advised, which will allow you to first select a lay-out in the "Comment display" referred to above, via:
- Structure >> Content Type >> Content type >> Comment display >> Layout for comment node content type
& will then allow fine-tuning of the fields in the comments.
The approving of the content by the admin; considering comments; can be tweaked via the row:
- People >> Permissions >> Comment >> Skip comment approval
Alternative modules for admin approval of general content can be found in the following StackExchange-post:
Just a final extra remark (more of an alternative easy work-around really): if the text format (cf. Configuration » Content authoring >> Text formats) to be used for your users allows for the HTML -tag, one can of course tell your users how to "post" (but not upload technically) images as a comment, by explaining that they could use <img src="URL">, like you can find explained e.g. @ the W3C-wiki or @ W3-schools.
P.S.: You are a funny guy to re-use Rome.
I will leave my original answer below, which is more applicable to letting people upload pictures as separate nodes; but (as described below) is not a good method for letting people upload multiple pictures to already existing nodes (as you have now updated your question).
Answer to your original question
What you can do is to create a new content type.
To do this, use the administrative overlay & go to:
- Structure >> Content Type >> Add content type.
Perhaps you could name the content type "Add a photo", or something.
Then, I would manage & display the fields such that all fields are hidden, except a field for a photo. This can usually be done after creating the content type, by going to:
- Structure >> Content Type >> Add a photo >> Manage fields.
- Structure >> Content Type >> Add a photo >> Manage display.
Then, I would restrict access to authenticated users (all of them / or some authenticated users; as you'd like) to create &/or edit certain content types only. This can be done (again, using the administrative overlay) by going to:
- People >> Permissions >> Add a photo: Create new content
- People >> Permissions >> Add a photo: Edit own content
The two boxes of these row can be checked at the column "AUTHENTICATED USER". (That is, if you'd like only authenticated users to be able to post pictures). Then, Creating & Editing of all the other content types should be disabled; if I understand you well. This can be done on the same page, by disabling the checkmarks for "AUTHENTICATED USER"s in e.g. the default content type "Article", via:
- People >> Permissions >> Article: Create new content
- People >> Permissions >> Article: Edit own content
This is just only what first comes to my mind. You'll see that Drupal is very flexible, and multiple roads lead to Rome.
