LiquidFractal

It is. All IPS apps has this feature from 4.1.18 onwards. 

There's actually a disconnect among all the content in all the apps but that's a larger discussion. Each app is a silo of information and is a problem that plagues a multi-app community.
The OP brings up a powerful example of a very unique weakness in the IPS suite.  Admins often have a fractured content base because images in IP.Board have no way of relating to images in IP.Gallery. It's a major, fundamental concern that I share as well.  
The OP shared one solution: to combine image content from forums and gallery into user content.  
I'm more a fan of generating a 'virtual' album in IP.Gallery where the images are linked from the forums.  
In any case, the cross promotion of content is one area that IPS hasn't even started to address but is a very real problem on complex multi app communities.  

I'm sensing a pattern in recent posts, and that pattern is: IPS Search could definitely use a major upgrade.

I'm sensing a pattern in recent posts, and that pattern is: IPS Search could definitely use a major upgrade.

I'm sensing a pattern in recent posts, and that pattern is: IPS Search could definitely use a major upgrade.

I'm sensing a pattern in recent posts, and that pattern is: IPS Search could definitely use a major upgrade.

I'm sensing a pattern in recent posts, and that pattern is: IPS Search could definitely use a major upgrade.

Putting my weight in here also.
I'm using Google Custom Search (CSE) on my site now as the built-in search is just terrible and the search result page was high on my sites Exit Pages. 
Adding to this the inability to search extra fields is just absurd and creates a strangle hold on a community market place that IPS are so keen to build up and improve.

I'm sensing a pattern in recent posts, and that pattern is: IPS Search could definitely use a major upgrade.

I'm sensing a pattern in recent posts, and that pattern is: IPS Search could definitely use a major upgrade.

I'm sensing a pattern in recent posts, and that pattern is: IPS Search could definitely use a major upgrade.

Agreed, if the field is important enough to be collected, it should be important enough to be able to be searched upon.  It is very limiting to not allow that and defeats the purpose of custom fields.

I got an extra field in Downloads, for example (this is a model, happens in any app), with option to search:

 
 
Then I got a file with this field filled:

 
 But when I search for something or here, I got nothing:

 
Also tried to search for:
here "something here" something here something+ here+  
How it should be?
Exactly like PROFILE FIELDS on Members search:

 
Those two (yelllow) fields are profile fields, so the user can search for them.
That doesn't happen on Extra Fields model. My Extra Field do not appear in the Advanced Search form:

No sign of the Extra Field there.
What's the point in allow the user to add a bunch of extra fields and do not retrieve records based on them?
I would like to request the addition of Extra Fields in the Advanced Search form, when the app uses it.
Thank you.