Pretty much any message could be a valid message in an SOA. It's all a question of where your service boundaries are.
Uploading a file is such a generic function that it's almost impossible to say. SOA is about defining proper service boundaries and contracts so that each service gets to be the unambiguous owner of all data associated with a particular business unit or business function. You don't specify whether there is supposed to be just one "file request", or many similar such types of requests belonging to different services, nor do you specify if uploading a file is a well-defined business capability or just something incidental to how a particular service might work. It's the answers to these last two questions that would tell you whether it fits the SOA model or not.
Be careful what you assume and/or read about SOA, there's a lot of steaming piles written on it by self-proclaimed gurus looking to make a quick buck off non-technical managers and enterprise architects by talking about Message Exchange Patterns that have been around since the original SOAP spec (or possibly since CORBA or even earlier). In practice, "good" SOA is largely about understanding how the business operates and specifically who owns what and how they're supposed to interact. Which MEPs you go with is hugely tied to what tools you use.
For example, in a strictly WCF architecture, "chunky messages" and callbacks are a normal everyday practice; on the other hand, in an ESB-based, pub/sub environment, request-reply messages (callbacks) are deeply disdained in favour of fire-and-forget, and bulky messages are something you want to avoid like the plague (especially in cloud computing environments where the message size limit is ridiculously small - you'd never get away with shoving an entire binary file in a single message!).
You have to tailor your MEPs to your tools. It's unproductive to ask about what messages are appropriate for an SOA. Ask about what service boundaries are appropriate for an SOA, and ask about what messages are appropriate for your specific tool set.