First you should probably identify what plants are there, including weeds, and how to keep them or destroy them.

Secondly, that plastic probably was some kind of liner or weed block at one time, meaning that whatever was on top (be it soil, mulch, etc) has either eroded away or decayed away. It would be good to redo it rather than just laying stuff on top again, including amending the soil if you're ready for that.

I say this also because it looks like it is currently as soil level, not below it. If you add more things on top, then you are overcoming the wood border near the fence as well as touching the wood portion of this building on the other side, which is dangerous for termites and other water problems.

Finally, depending on the direction this area is facing and its level of light in regards to sunlight, then you can get other recommendations on new plants and/or bushes that you might want to plant there.

I just happened upon your post. If this was my yard, I'd take out all that plastic and do something like this. Depends on where you are, what direction your yard faces, etc. But a local garden center could help you replicate it with appropriate ground covers. You could ask for help i.d.ing the plants that are there and you could leave anything choice, or just take it all out and add new.

I have found an article about Garden Restoration Projects. You can check it out for ideas on how to properly restore your garden.

Here is a link that might be useful: Great Garden Restoration