The reason we impose size limits on images has nothing to do with rank. If we allowed some ranks to upload "triple the size limit" of images, and disallowed other ranks, the end result would still be the same: images across the site would be larger and have a larger filesize, and a larger filesize is what we don't want. Let me explain why.
Images (photos, logos, etc.) are among the biggest bandwidth users on websites, compared to the code involved in retrieving data from a database. The filesize of images can be astronomical in comparison. Now, when you visit a page on MA your browser is retrieving the data on the page you're viewing. As the page loads, it runs the code, issues queries on the database and displays any data and images to you. In very simple terms, this is bandwidth. Each time you load a page (especially for the first time) this process begins anew. Over and over again, more data is requested from the site's server with images using up the most bandwidth due to their size. Multiply this by the thousands, if not hundreds of thousands of hits an individual page might get in a day, or a week, or a month, and bandwidth adds up quickly and substantively. Don't be alarmed by this - MA can certainly handle everything you can currently throw at it - but the process is one every site (and server) you visit goes through.
Servers restrict how much bandwidth a site can use in a given pay period. On top of that, the more hits (requests) that the server receives by individuals like yourself who use up bandwidth, the more likely you could congest the server to the point that requests from others are interrupted and the site is slow or "down." This is, in essence, one of the mechanisms behind a denial-of-service attack, when done deliberately. It is true that nowadays it's unlikely for this to happen; network bandwidth is usually better and there's more ways to mitigate congestion. That said, not all sites are created equally (or served equally) and so if you want more bandwidth, you need to pay more...
... And that's the other thing to keep in mind. I can certainly agree that it would be nice to have larger images or be able to host multiple logos or photos or whatnot. It sounds wonderful... but there's a cost, and that cost is financial. Are larger images worth an increased cost? Truthfully, that's not really our prerogative to ask that, as you and I don't pay for it. The owners might feel obliged to say yes or no, but this is not something we as visitors and volunteers can promulgate on their behalf. But, for such an ultimately aesthetic improvement, I can't see it being a convincing priority, personally.
So, in short, someday - maybe - there might be an increase in image size (who knows?), but understand that the reasoning for keeping the size limits as they are is not arbitrary. It's not just a matter of restricting use.