Not something I know much about, but your code (I only glanced at it, so may have wrong end of the stick ...) looks like you are storing the image data in chunks:
For iChunks = 1 To lChunks
Get nHandle, , aChunk()
lOffset = lOffset + conChunkSize
Back in Old Versions of SQL the IMAGE datatype (and also TEXT for any string columns more than 8,000 characters) had to be stored in that way. But nowadays that isn't necessary because of new datatypes varbinary(MAX) (and varchar(MAX) for large strings). So if you are using IMAGE datatype (which is deprecated) change that to varbinary(MAX) instead.
(There may still be limitations because of ODBC etc. layer between your APP and SQL, or if "that's the way that Access does it" etc.)
Make sure you use separate tables for Images (don't put the Employee image in the Employee table, use a separate table joined on EmployeeID), and put that in separate file group
Worth just posing the question of whether (in your situation) its a good idea to store the images in the DB at all. There are pPROs and CONs which you can Google, but the main ones that occur to me are:
If images are large / numerous they bloat the database, stored in all backups, and moved around with the DB (e.g. a DEV, TEST, QA versions of the DB). But that can be a good thing too - the backup always contains all the images
If you want to use the image on a Web Page it is mostly likely to be more efficient just to have it on disk so the URL can retrieve it from there.
Putting an image IN the DB means that it can be part of a transaction - so the Employee AND Image are wither both there, or neither are, you won't get someone accidentally deleting the image from disk, or there being an Image left over when an Employee record is deleted. But I think that SQL FILESTREAMS can also achieve that (with images on Disk)
If you put the image on disk, instead, then just store the path/filename in the DB (that is short, so would be OK to put IN the Employee table).
I've seen articles that say that images up to 256K stored in DB is good, and above 1MB consider storing in files. For images only used on Web Pages / APPs I would still favour the files approach.
The way I handle that (but don't know how easy that is to code-behind a button in Access?)
Let's say that my PKey is EmployeeID and the current record I am looking at is EmployeeID=1234
To get the next record I would do
SELECT TOP 1 EmployeeID, EmployeeName, ...
WHERE EmployeeID > 1234
ORDER BY EmployeeID
Make sure (for performance) that you have an index on EmployeeID - usually in this situation that will be the Clustered Index, but doesn't have to be of course.