Try the following macro - it will delete all graphics while leaving your other formatting alone.
Code:
Sub DeleteGraphics()
Application.ScreenUpdating = False
Dim Rng As Range
With ActiveDocument
For Each Rng In .StoryRanges
With Rng
While .InlineShapes.Count > 0
.InlineShapes(1).Delete
Wend
While .ShapeRange.Count > 0
.ShapeRange(1).Delete
Wend
End With
Next
End With
Application.ScreenUpdating = True
End Sub