Using Folders for Organization
Advantages: They are logically clear to someone fiddling with the system on the back end- that's about it really.
Disadvantages: 'harder' to clean up when you delete a company, etc. and you have to make sure none of your directory names overlap, generally more work from the get go.
Using Images in One Folder
Advantages It's technically a bit easier to clean up and not all that much work.
Disadvantages You'll have to write at minimum a very basic collision detection algorithm and a very basic 'random name generator'.
Using the Database to Store Images
Caution: Many lives have been lost in this argument!
Advantages: Referential integrity, backing up/restoring is simpler, categorization
Disadvantages: Fraught with pitfalls, potentially slower, more advanced storage/retrieval techniques, potential performance issues and increase of network requests. Also, most cheap hosting providers' databases are way too terrible for this to be a good idea.
I highly recommend just using a hashed file name and storing it (the filename) in the database and then storing the images in a folder (or many folders) on disk. This should be much easier in the long run and perform better in general without getting too complicated.