Here is an up-to-date list of challenges from the past. I couldn't find a reference to challenge 216 though.
231 Concert
230 Tales from the riverbank
229 Anthropomorphism
228 Vintage
227 Urban Landscape
226 Neglected
225 As Time Goes By
224 Christmas
223 Snow
222 Autumnal
221 Fieldscape
220 Incongruous
219 Superfluous
218 Misty Moisty Morning
217 Ambiguous
216 ?
215 Closes, wynds, snickets alleys
214 Runs on rails
213 Ye Olde Worlde
212 Blend
211 Tents
210 Festival
209 Bill No-Mates
208 Fast Food
207 Subtle Self
206 Big Dog
205 Adventure
204 Fences
203 Weather
202 Stones
201 Minimal
200 On display
199 Blimet, it's cold out there!
198 Worker
197 Road(s)
196 ?
195 Summer
194 Root and branch
193 Threads
192 Something a person is wearing that makes them look amusing
191 Dancing
190 Flat
189 Twist, turny
188 Droughty, dry or dehydrated
187 Slap Bang Wallop
186 Towers
185 Militaria
184 Lighthouse
183 Down on the Farm
182 Run
181 Intentional Camera Movement
180 Triangle
179 Spring has Sprung
178 Two Wheels
177 Workplace
176 Image for a magazine / book cover
175 Night-time
174 Holes
173 Places of Worship
172 Tracks
171 Wrack and Ruin
170 Street Furniture
169 Three / Triple / Trio
168 Unintentional Camera Movement
167 Only the lonely
166 Whatever the Weather
165 Beside the seaside, beside the sea
164 Album Cover
163 BAD
162 Geometric
161 Alleys
160 Into the Light
159 Opening
158 Down
157 Benches
156 Cafe
155 Cats and Dogs
154 Overgrown
153 Boats
152 Song Title
151 Diorama
150 Shopping
149 Rubbish, Trash and Garbage
148 Parent and Child
147 Test Shot
146 Hero
145 Singular
144 Collection
143 Misty
142 Fun
141 In Memoriam
140 Distance
139 Slow
138 Be Kind
137 Looking Up
136 Hats
135 Things fall apart; the centre cannot hold
134 Above
133 Locked
132 Narrow
131 Daytrip
130 Crossed
129 Opposites
128 Doors
127 Relax
126 Happier Days
125 Community
124 Pub Lunch
123 Bottoms
122 Leaves or Leaf
121 Small
120 The Picnic
119 I'll drink to that
118 Never leave home without it
117 Old Flame
116 Happy Accidents
115 Designed Water
114 Silhouette
113 Transport
112 Through the Window
111 Hut(s)
110 In the Shade
109 Gone shopping
108 Bells and Whistles
107 Lines
106 Animal
105 Down by the river
104 Crowded
103 Feet
102 Urban Landscape
101 Waves
100 Landmark
99 CAPITAL
98 Summer will soon be here!
97 Nostalgia
96 Corners
95 Fruit
94 Pairs
93 Food and Drink
92 Sporty
91 Misty
90 DECAY
89 BLUE
88 Fall(s)
87 Phew What a Scorcher..."
86 Gone But Not Forgotten'
85 THE CASTLE
84 Recycling
83 SPEED
82 LONG
81 Architecture
80 On The Beach
79 All Creatures Great & Small
78 Festiv(al)
77 Work, work, work!
76 Communicate
75 Illuminate
74 Show Us Your Best Abstract Shot
73 Reflections
72 Autumn
71 Music to my ears
70 Beer and Brewing:
69 Waterfalls, weirs and cataracts.
68 Being Cool!
67 Bingo !!
66 Take Off!
65 Chairs -
64 Chiaroscuro
63 The Postal System
62 Spooky
61 STATUES
60 Street Art
59 Harbour
58 You
57 Flowers
56 Shafts of light
55 Beach
54 The Photographer
53 Celebration
52 Moving
51 Bridge
50 Pairs
49 ...seen better days!
48 Birds Eye View
47 The Decisive Moment
46 Post your Diptych
45 One from the wall
44 Citius, Altius, Fortius
43 Multiple Exposure
42 In or Out
41 You and Yours
40 Fire!
39 Life's a beach
38 TREES
37 Over Hill, Over Dale
36 You've been framed
35 Any Old Iron
34 CURVES
33 MONUMENTS
32 Dead, dying or decaying
31 Green
30 Keep on moving!
29 Elevated
28 Sunny
27 Water
26 Spring
25 blue
24 Kids
23 Cityscape
22 Storm
21 A day in the life
20 Sunset
19 Clouds
18 Plants and flowers.
17 Triangles (real or implied)
16 Reflection
15 Ships and Boats
14 The New And The Old In One Shot
13 Artistic Performance
12 Animals
11 Cars
10 DARK
9 Bridges
8 Good old days
7 Fiat Lux
6 Human Powered Vehicle
5 Sporting Shot
4 Christmas Shot
3 Power
2 Holiday Photograph
1 Architectural Icon
