If you want to open the image in your native image viewer, try os.startfile:
import os
os.startfile('file')
Or you could set the image as the background using a GUI library and then show it when you want to. But this way uses a lot more code and might impact the time your script takes to run. But it does allow you to customize the ui. Here's an example using wxpython:
import wx
 
########################################################################
class MainPanel(wx.Panel):
    """"""
 
    #----------------------------------------------------------------------
    def __init__(self, parent):
        """Constructor"""
        wx.Panel.__init__(self, parent=parent)
        self.SetBackgroundStyle(wx.BG_STYLE_PAINT) # Was wx.BG_STYLE_CUSTOM)
        self.frame = parent
 
        sizer = wx.BoxSizer(wx.VERTICAL)
        hSizer = wx.BoxSizer(wx.HORIZONTAL)
 
        for num in range(4):
            label = "Button %s" % num
            btn = wx.Button(self, label=label)
            sizer.Add(btn, 0, wx.ALL, 5)
        hSizer.Add((1,1), 1, wx.EXPAND)
        hSizer.Add(sizer, 0, wx.TOP, 100)
        hSizer.Add((1,1), 0, wx.ALL, 75)
        self.SetSizer(hSizer)
        self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnEraseBackground)
 
    #----------------------------------------------------------------------
    def OnEraseBackground(self, evt):
        """
        Add a picture to the background
        """
        # yanked from ColourDB.py
        dc = evt.GetDC()
 
        if not dc:
            dc = wx.ClientDC(self)
            rect = self.GetUpdateRegion().GetBox()
            dc.SetClippingRect(rect)
        dc.Clear()
        bmp = wx.Bitmap("file")
        dc.DrawBitmap(bmp, 0, 0)
 
 
########################################################################
class MainFrame(wx.Frame):
    """"""
 
    #----------------------------------------------------------------------
    def __init__(self):
        """Constructor"""
        wx.Frame.__init__(self, None, size=(600,450))
        panel = MainPanel(self)        
        self.Center()
 
########################################################################
class Main(wx.App):
    """"""
 
    #----------------------------------------------------------------------
    def __init__(self, redirect=False, filename=None):
        """Constructor"""
        wx.App.__init__(self, redirect, filename)
        dlg = MainFrame()
        dlg.Show()
 
#----------------------------------------------------------------------
if __name__ == "__main__":
    app = Main()
    app.MainLoop()
(source code from how to put a image as a background in wxpython)
You can even show the image in your terminal using timg:
import timg
obj = timg.Renderer()                                                                                               
obj.load_image_from_file("file")
obj.render(timg.SixelMethod)
(PyPI: https://pypi.org/project/timg)