This macro will allow you to select the desired image and then paste it to the ACTIVECELL.
You could modify the macro slightly for your purposes (currently it is restricted to L5), then call the macro from your USERFORM. The user will need to select the cell where the image shall be pasted prior to running the macro.
Code:
Option Explicit
Sub ChangeImage()
Application.ScreenUpdating = False
With Range("L5")
ActiveSheet.Pictures.Delete
End With
With Application.FileDialog(msoFileDialogFilePicker)
.AllowMultiSelect = False
.ButtonName = "Submit"
.Title = "Select an image file"
.Filters.Clear
.Filters.Add "JPG", "*.JPG"
.Filters.Add "JPEG File Interchange Format", "*.JPEG"
.Filters.Add "Graphics Interchange Format", "*.GIF"
.Filters.Add "Portable Network Graphics", "*.PNG"
.Filters.Add "Tag Image File Format", "*.TIFF"
.Filters.Add "All Pictures", "*.*"
If .Show = -1 Then
Dim img As Object
Set img = ActiveSheet.Pictures.Insert(.SelectedItems(1))
With Range("L5")
img.Top = .Top
img.Width = 90
img.Height = 90
img.Left = .Left
img.Placement = xlMoveAndSize
End With
Else
MsgBox ("Cancelled.")
End If
End With
Application.ScreenUpdating = True
End Sub