|It can handle what you are talking about as long as YOU are very organized.|
First gedcoms - gedcoms are not designed to 'carry' pics and other media - if yours do, it is a special progamming feature from your manufacturer. It probably is using a standard gedcom area that is not used much to do this. Gedcoms will carry media links and some systems will let you load an entire media folder with links in the gedcom to that folder . Tribal Pages doesnot work this way so you will have to attach each photo individually.
Also , loading a new gedcom completely wipes out the previous gedcom. This is where the discipline comes in.
You can either keep your master file resident on your computer or you can keep it on TribalPages. I use a master resident on my computer and only allow my 'user group' to add details, photos and correct errors. I reserve all adding of people to myself.
Other keep the master online and let their users add to it. Then when they need to update their home file they download the backup from tribalpages and use it. But you really have to make the choice when you start up.
The biggest drawback for me is the limited number of sources that can be used and some custom events don't work well.
Having said all that - I love TP, It can handle enormous numbers of individuals and pictures. My users are scattered over 5 continents and they all like the photos and ease for editing. I can custom set their permissions and privacy and they work well.
I don't know what you mean be large . I know that TP can easily handle tens of thousands - I'm not sure about hundreds of thousands.
Hope this helps