In theory, the only limit is the 2Gig limit that Access has. But, to me that would be too big simply because it is cumbersome to distribute and performance would probably be pretty slow with a FE that grew to that size.
But as to say 10meg is too large, or 50meg is too large is too black & white for me. Your FE has to be the size required to perform to the specification desired. If you want a bunch of graphics embbeded in your FE to add to the user experience, then so be it, but your file size will be larger. If you require 1000 querydef objects to acheive the functionality you need, then fine. But what I don't encourage is the use of the FE as a Datastore. For example, if your app utlizes Temp Tables, don't bring those tables to the Front End, just create a temp database that you can used to dump data into, and then link to the temp db. I fully subscribe to the concept of keeping your data and the application objects (the FE) completely separate.
As a point of reference, one of the largest FE's I have created is about 17meg, no embeded pics.... it is a pretty significant application, here are the stats:
Tables: 139
Queries: 201 (large portion are Passthrough to SQL Server BE)
Forms: 126
Modules: 42
Reports: 141
LinesOfCode: 28247