How about a SF time capsule ?

[Iodine]

I'll throw in my computer mouse and one of my old Ricky Nelson cassettes.

 

[MarciKS]

I'll add my barrel. LMBO!

 

[Fyrefox]

A complete and extensive history of the year 2020 should be included to make any future observers grateful that humanity had endured to reach the age that they were in...

 

[Lewkat]

I'd put in some iconic music such as Gershwin's Rhapsody In Blue and Glen Miller's Moonlight Serenade. Both should have been included in that space explorer.

 

[Meanderer]

Cartoons are timeless, so a few cartoons, for sure!

 

[Pappy]

I would throw in 2020..... , but really, an old piano roll, you know player piano things that play music when you pump your guts out.
Maybe a floppy disc or a tube tv.