Yes. it is relatively flat in comparison to the Lakes, but there is plenty of good countryside around. As well as the Wolds, which can be very beautiful, there is the River Witham which runs all the way down to Boston. There is a great track for walking or cycling along it called the "Water Railway" (it is based on the old railway track that ran there). Lots of opportunities for photography along there. There are also quite a lot of woods, eg Bardney Limewoods, Chambers Farm Woods to name but 2 within a couple of miles of where I live. Also worth checking out are the sites of the Lincolnshire Wildlife Trust, eg Gibraltar Point, Snipe Dales. Additionally Lincolnshire is littered with small back roads which give you plenty of opportuntiy to stop and find new and diiferent things to photograph. The only thing to be careful about on the roads is tractors which run on all, including the main roads as it is an agricutural county, and heavy lorries are needed to move the produce to market. Areas round the south of the county may appear flat, but that does not mean they are devoid of scenery. Around Spalding, Holbeach, Bourne, out towards the coast and down towards the Norfolk border there is a lot to see. The population is very scattered and so communities are often very small, so small groups have their own character and photographs of different areas can be very interesting. For example we live in a small off road community of 10 people only, surrounded by SSSIs and farmland. There are also many old and historical houses, churches and abbeys (mostly in ruins), but they provide a wealth of opportunity for photography.
Since my wife and I took up photography as a hobby rather than a sideline business we have developed a great interest in wildlife, birds and insects, of which there are many over the whole of the county. In our garden it is not unusual to see kestrels, woodpeckers, partridges, pheasants, tits of all varieties, many different finches, blackbirds, sparrows, starlings, all sorts of doves, insects of all types (eg butterflies, dragonflies, damselflies, bees, hornets); we even have deer, foxes, rabbits, hares that come quite regularly. You should not be starved for photographic interest, you just need to stop and wonder at the beauty of nature.