I'm able to fix my own problem, I added "N" in my SQL Statement, from
sqlRun = "UPDATE Bioser SET Singature = (SELECT * FROM OPENROWSET (BULK '" & Server.MapPath("signatures\"& Transcode &".bmp") & "', SINGLE_BLOB) as Singature) WHERE ServiceNo = '" & Transcode & "'"
I revised it as:
sqlRun = "UPDATE Bioser SET Singature = (SELECT * FROM OPENROWSET (BULK N'" & Server.MapPath("signatures\"& Transcode &".bmp") & "', SINGLE_BLOB) as Singature) WHERE ServiceNo = '" & Transcode & "'"
I forgot that I need the N for converting the image base64 string to UNICODE (NVARCHAR/NCHAR). And my code is now working again. Yay!