Well, in my city there is the "Academia de Caballeria", there are a lot of military uniforms from different times...
Spain has had many militar uniforms, even nowadays each 28 of may it's the Spanish army day, and they march with classical uniforms. Exactly between 1914-18 i don't know, you can see something related to the Rif War and the uniforms of the "Regulares", they were from that time.
Btw, Spain was a poor country because the Napoleonic wars suposed the independence of the colonies and the country was prettty much split after that, causing a huge inestability in the XIX century, with many revolutions and civil wars (3 Carlist wars), and at the end of that century the Spanish-American War.