ASP Code to update field using SP (text field)

We had a field which was nvarchar 8000, it was changed to a text field to accomodate more characters.

I currently have the code below to call the Stored Procedure, but the parameter is for 8000 characters, how should I change it to allow the entry of as many characters as the text field allows?

<%

Set UpdateSignature = Server.CreateObject ("ADODB.Command")
UpdateSignature.ActiveConnection = MM_bluedot_STRING
UpdateSignature.CommandText = "UPDATE Userlogin SET Emailsignature = ? WHERE  userid = ?"
UpdateSignature.Parameters.Append UpdateSignature.CreateParameter("MMColParam", 200, 1, 8000, MM_IIF(Request.Form("signature"), Request.Form("signature"), UpdateSignature__MMColParam & ""))
UpdateSignature.Parameters.Append UpdateSignature.CreateParameter("MMColParam2", 3, 1, 4, MM_IIF(Session("Userid"), Session("Userid"), UpdateSignature__MMColParam2 & ""))
UpdateSignature.CommandType = 1
UpdateSignature.CommandTimeout = 0
UpdateSignature.Prepared = true
UpdateSignature.Execute()

%>

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Something else that may be relevant is that this field is intended to save the user's signature block, if they add an image (their logo) then the HTML editor converts it into characters and this is where 8000 characters don't seem to be enough.
I am not sure if because we are including an image I may need to use a different type of data for the user, otherwise I guess text fiedl will work.