I was one participant from Ukraine (I think so) so I chose a topic related to the territory of Ukraine. All this was created using open source software and open data created by OpenStreetMap contributors without the use of commercial software.

I used: QGiS, GRASS GIS, SAGA GIS, GDAL, Python, Blender, Inkscape, GIMP and Ubuntu 18.04.

Kyiv traffic light (signals)
Data: OpenStreetMap contributors, QGIS

Part of Eastern Beskyds, Chornohora (Black Mountain)
Thanks for the tutorial @imhere_asia You're great!
Data: Alaska Satellite Facility, QGIS

Isochrones map by time on cars between cities Lutsk an Rivne, Ukraine.
on the left is Lutsk - Population: 217,103
on the right is Rivne city - Population: 247,356
Data: OpenStreetMap contributors, QGIS

Density of restaurants, bars and cafes in Lviv (Ukraine)
Data: OpenStreetMap contributors, QGIS

The northern part of the Black Sea in winter, 2018.
Created with combination True Color Band (4+3+2) and False color IR composite (8+4+3) for land, Inverted True Color and Inverted Infrared bands for water.
Data: SENTINEL-2A European Space Agency - ESA

Between the cities of Dnipro and Zaporizhia, Ukraine.
Data: Sentinel2
p.s. Rapids is not on the map, they are underwater ;)

Dnipro city. Relief
Data: Alaska Satellite Facility, OpenStreetMap contributors

Green Kharkiv. Public green space.
Data: OpenStreetMap contributors

Center-pivot irrigation fields of Kherson region
Data: Sentinel2, qgis, gimp2

Black & White Ternopil city
Data: OpenStreetMap contributors, qgis

Vihorlat-Gutin Area part of the Inner Eastern Carpathians
Data: SRTM, OpenStreetMap contributors, qgis

Vinnytsia Public Transport Abstract Model
OpenStreetMap contributors, qgis

Poltava. Public GPS Track
Visitors and residents create their own urban fabric.
OpenStreetMap contributors, qgis

Ivano-Frankivsk. City center pedestrian zone boundaries
Data: OpenStreetMap contributors qgis

Chernivtsi. City neighborhood names (Voronoi decomposition).
OpenStreetMap contributors, qgis, grassgis

Sumy oblast (region), Northeast Ukraine. Region with the largest number of hamlets.
Map based on density and map based on population size with loss.
OpenStreetMap contributors, qgis

Flower of wormwood (Artemisia vulgaris)
The Chernobyl Nuclear Power Plant Zone of Alienation
Based on my old project
Data: OpenStreetMap contributors, qgis

World Stereographic. EPSG:54026
Data: Natural Earth Data v.4

Year of construction of buildings in Lviv, Ukraine.
Shaded according to year of construction buildings in the center of city.
Lviv was founded of the 13th century.
Data: OpenStreetMap contributors, qgis

River Zbruch millennial natural border. I tried to show the typical structure Podolia countryside.
Left side Ternopil region, right Khmelnytsky region of Ukraine.
Podolia or Podilia is a historic region in Eastern Europe, located in the west-central and south-western parts of Ukraine and in northeastern Moldova (i.e. northern Transnistria).
Data: OpenStreetMap contributors, qgis

Protected areas in Volyn region, Ukraine. Based on Openstreetmap contributors data
Data: OpenStreetMap contributors, qgis

Built environment around Mykolaiv, Ukraine.
Data: OpenStreetMap contributors, qgis

Map of depopulation of Ukrainian SSR in 1933.
Today's theme of the MapChallenge is related to the population.
Today is the Holodomor Remembrance Day In Ukraine.
So I created this map. More http://gis.huri.harvard.edu/historical-atlas/the-great-famine.html
Data: Ukrainian Research Institute at Harvard University,
Ukrainian Institute of National Remembrance «The Memorial to Victims of the Holodomor» National Museum

Abstract statistics on fertility, mortality and migration processes for the first part of 2019
in some regions of Ukraine.
Data: OpenStreetMap contributors, qgis, ukrstat.gov.ua

Isoterm of average temperature in Ukraine.
Data: WorldClim Version2, qgis, sagagis

Watershed area of small river Kovray (Cherkasy region, Ukraine) and stream detection.
Data: SRTM, OpenStreetMap contributors
SAGA GIS, QGIS

Open-pit mining in the Dnipropetrovsk Oblast. Kryvorizkyi Iron Ore Basin (Kryvbas)
Data: OpenStreetMap contributors, qgis

Guillaume Le Vasseur de Beauplan
«Delineatio Generalis Camporum Desertorum vulgo Ukraina. Cum adjacentibus Provinciis».

The main feature - oriented to the south.

Data: OpenStreetMap contributors, qgis

Note: the first edition of the map was created 380 years ago. This map is just the first prototype. This Challenge outlined directions for my future development. So there are many prototypes here. Every day, a new prototype isn't so bad ;) Of course, achieving the skill with which this series of maps was created is not an easy task. But I will try;)

Fragment of the Ros river basin.
Data: Alaska Satellite Facility, OpenStreetMap contributors

The City of Cherkasy. Perspective view without relief.
Data: OpenStreetMap contributors
QGIS, Blender, Inkscape

OSM: Perspective view of Cherkasy is the "OpenStreetMap Featured Image" on Week 50 (from Monday 9 December 2019 to Sunday 15 December 2019) !: https://wiki.osm.org

Texty.org.ua (in Ukrainian): Колекція захоплюючих карт про Україну (ІНФОГРАФІКА) http://texty.org.ua/pg/news/devrand/read/98373