Take a look at what your code is doing here:
    Set oTbl = Selection.Tables.Add(Range:=Selection.Range, NumRows:=2, NumColumns:=NumCols)
    Dim orng As Word.Range
    Set ornge = ActiveDocument.Range.Bookmarks("pretestpics").Range
    ActiveDocument.Bookmarks.Add "pretestpics", oTbl.Range
you say you already have the bookmark, but you're not using it as the location to insert the table. You're evidently not using Option Explicit, either, as you Dim orng but Set ornge (both of which are unnecessary, anyway, as is the next line).

PS: When posting code, please post formatted code and use the code tags, indicated by the # button on the posting menu. Without them, your code loses much of whatever structure it had.